Herb & supplement monograph

Chlorella Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by ·Updated July 2026
What is this page for?

First and foremost: how Chlorella interacts with medications. The heart of this page is the interaction list — every drug Chlorella is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Chlorella is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Chlorella Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Chlorella drug interaction appears low for most people, though a couple of situations deserve real attention. None of the listed interactions are rated major, and the concerns that exist rest on case reports and theory rather than well-controlled human studies.

Interactions deserving the most attention

The interaction that matters most involves warfarin. Chlorella naturally contains a good amount of vitamin K, which works against this blood thinner, and there is a case report of warfarin becoming less effective after someone started chlorella. Because warfarin is a narrow-margin medicine where small changes can affect clotting, this combination deserves close attention. Chlorella has also been reported to make skin more sensitive to sunlight, so pairing it with photosensitizing drugs could add to that effect.

What the rest of the list means

The long list of interacting medications mostly reflects how many drugs fall into these two broad groups, not hundreds of separate proven problems. The evidence behind these concerns comes from a handful of case reports and theoretical reasoning, so a predicted effect will not necessarily play out in every person taking one of these medicines.

Check your medications against Chlorella

Based on HelloPharmacist’s Chlorella interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Chlorella

337 medications have a known interaction with Chlorella, graded by severity. Select any drug for the full evidence-based detail.

2,830 drugs
AcepromazineAtravet
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acepromazine interaction
Acetaminophen, Brompheniramine, PhenylpropanolamineDimetapp Cold and Flu
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Brompheniramine, Phenylpropanolamine interaction
Acetaminophen, Caffeine, Chlorpheniramine, Hydrocodone, PhenylephrineHycomine Compound
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Caffeine, Chlorpheniramine, Hydrocodone, Phenylephrine interaction
Acetaminophen, Chlorpheniramine Maleate, Dextromethorphan HbrVicks Formula 44M Cough, Cold & Flu Relief
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine Maleate, Dextromethorphan Hbr interaction
Acetaminophen, Chlorpheniramine, Codeine, PhenylephrineColrex
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Codeine, Phenylephrine interaction
Acetaminophen, Chlorpheniramine, DextromethorphanCoricidin II Extra Strength Cold and Flu
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Dextromethorphan interaction
Acetaminophen, Chlorpheniramine, Dextromethorphan HydrobromideCoricidin HBP Maximum Strength Flu
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Dextromethorphan Hydrobromide interaction
Acetaminophen, Chlorpheniramine, Dextromethorphan, PhenylpropanolamineMulti Symptom Cold Relief
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Dextromethorphan, Phenylpropanolamine interaction
Acetaminophen, Chlorpheniramine, Dextromethorphan, PseudoephedrineChildren's Tylenol Cold Plus Cough, Tylenol Cold Ex Strength
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Dextromethorphan, Pseudoephedrine interaction
Acetaminophen, Chlorpheniramine, Guaifenesin, Phenylephrine, SalicylamideRhinogesic GG
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Guaifenesin, Phenylephrine, Salicylamide interaction
Acetaminophen, Chlorpheniramine, PhenylephrineAlka-Seltzer PLUS, Histex SR, Protid
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Phenylephrine interaction
Acetaminophen, Chlorpheniramine, Phenylephrine, SalicylamideRhinogesic, Rhinogesic JR
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Phenylephrine, Salicylamide interaction
Acetaminophen, Chlorpheniramine, PhenylpropanolamineAlumadrine, Conex, Sinadrin Max Strength, Sinulin
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Phenylpropanolamine interaction
Acetaminophen, Chlorpheniramine, Phenylpropanolamine, OpiumHista-Derfule
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Phenylpropanolamine, Opium interaction
Acetaminophen, Chlorpheniramine, Phenylpropanolamine, PhenyltoloxamineNorel Plus
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Phenylpropanolamine, Phenyltoloxamine interaction
Acetaminophen, Chlorpheniramine, PseudoephedrineAlka-Seltzer PLUS Liquid Gels, Children's Tylenol Cold, Codimal, Comtrex, Extra Strength Tylenol Allergy Sinus, Lorsin +3 more
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Chlorpheniramine, Pseudoephedrine interaction
Acetaminophen, Dexbrompheniramine, PseudoephedrineSinadrin Plus
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Dexbrompheniramine, Pseudoephedrine interaction
Acetaminophen, DiphenhydramineTylenol PM, Tylenol PM Ex Strength
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Diphenhydramine interaction
Acetaminophen, Diphenhydramine, PseudoephedrineChildren's Tylenol Allergy, Cold Control, Contac Night Allergy Relief
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Diphenhydramine, Pseudoephedrine interaction
Acetaminophen, IbuprofenCombogesic
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Ibuprofen interaction
Acetaminophen, Phenylephrine, ChlorpheniramineSuper Cold Tabs
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetaminophen, Phenylephrine, Chlorpheniramine interaction
AcetazolamideAk-Zol, Diamox
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetazolamide interaction Acetazolamide drug page: uses, dosage & side effects
AcetohexamideDymelor
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acetohexamide interaction
AcitretinSoriatane
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Acitretin interaction Acitretin drug page: uses, dosage & side effects
Alectinib HydrochlorideAlecensa
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Alectinib Hydrochloride interaction Alectinib Hydrochloride drug page: uses, dosage & side effects
AlitretinoinPanretin
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Alitretinoin interaction Alitretinoin drug page: uses, dosage & side effects
Amiloride, HydrochlorothiazideAmil-Co, Amilzide, Moduret 25, Moduretic
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Amiloride, Hydrochlorothiazide interaction Amiloride, Hydrochlorothiazide drug page: uses, dosage & side effects
Aminolevulinic Acid HydrochlorideAmeluz, Gleolan
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Aminolevulinic Acid Hydrochloride interaction
AmiodaroneCordarone, Pacerone
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Amiodarone interaction Amiodarone drug page: uses, dosage & side effects
AmitriptylineElavil
Moderate Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.

Read the full Chlorella + Amitriptyline interaction Amitriptyline drug page: uses, dosage & side effects
Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

  • Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
  • Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
  • Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
  • No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

  • Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
  • Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
  • Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

  • Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
  • Each drug listed above links to the full report for that exact Chlorella combination — clinical detail, likelihood, evidence level, and citations.
  • Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.
The big picture

The kinds of drugs Chlorella affects

Every type of medication (drug category) Chlorella is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 2 drug categories Chlorella interacts with
Photosensitizing DrugsWarfarin (coumadin)
Photosensitizing Drugs

Theoretically, chlorella might have additive effects with photosensitizing drugs.
Chlorella has been reported to cause photosensitization. In five case reports, patients who had ingested chlorella exhibited swelling followed by erythematopurpuric lesions on sun-exposed areas of the body. Theoretically, concomitant use with photosensitizing drugs may exacerbate effects.

Likelihood Possible Evidence D
Warfarin (Coumadin)

Theoretically, chlorella might reduce the clinical effects of warfarin.
Chlorella contains significant amounts of vitamin K. There is at least one case report of warfarin therapy becoming sub-therapeutic after initiation of chlorella supplements.

Likelihood Possible Evidence D
Monograph

Chlorella: Uses, Safety & Side Effects

Medically reviewed by · Reviewed July 2026 ·
The bottom line

Chlorella is a nutrient-rich freshwater green algae taken as a supplement for general wellness, immune support, and 'detox.' Some small studies suggest possible benefits for cholesterol, blood pressure, and immune markers, but the overall evidence is limited and not strong. It is generally well tolerated, but quality varies and it should be avoided during pregnancy and breastfeeding unless a doctor approves.

Chlorella
Scientific name
Chlorella vulgaris
Family
Chlorellaceae
Part used
Whole dried algae cells
Common forms
Tablets, capsules, powder, extract, and liquid
People commonly use it for
  • General nutrition and 'detox' support
  • Immune support
  • Liver and kidney support
  • Antioxidant and anti-inflammatory support
  • Cholesterol and heart health

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance
OverallUse caution

Generally well tolerated short term, but product quality and purity vary widely.

PregnancyPossibly Safe

When used orally and appropriately in medicinal amounts for up to approximately 28 weeks. A commercially available chlorella supplement (Sun Chlorella...

Read the full pregnancy detail
BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Chlorella is a type of single-celled green algae that grows in fresh water. It has been used as a food and supplement for many years, especially in Japan and other parts of Asia. Because it is rich in nutrients, it is often marketed as a 'superfood.'

Chlorella naturally contains a mix of vitamins, minerals, protein, fiber, and plant pigments such as chlorophyll, lutein, and zeaxanthin. The exact nutrient content depends on the species, how it is grown, and how it is processed. The tough outer cell wall is usually 'cracked' or broken during manufacturing so the body can absorb the nutrients better.

People take chlorella for many reasons, including general nutrition, immune support, and so-called 'detox.' It is sold as tablets, capsules, powders, and liquids.

How it works

Chlorella contains many compounds that could explain its proposed effects. These include chlorophyll, carotenoids (such as lutein and zeaxanthin), protein, fiber, and various vitamins and minerals.

Researchers think the antioxidant pigments may help reduce oxidative stress, while fiber and other compounds might affect cholesterol and blood sugar. Some studies suggest it may influence immune cells, and laboratory work has looked at whether the cell wall can bind certain toxins or heavy metals.

It is important to know that most of these mechanisms come from laboratory and animal studies. How well they apply to people taking chlorella is not yet clear.

Effectiveness

Does Chlorella work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by .

Evidence overview · 15 uses evaluated
1 Possibly effective 14 Insufficient evidence
How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.
2Likely EffectiveGood evidence, though not yet conclusive.
3Possibly EffectiveSome evidence suggests a benefit.
4Possibly IneffectiveSome evidence it may not help.
5Likely IneffectiveFairly strong evidence it doesn’t help.
6IneffectiveStrong evidence it doesn’t work.
7Insufficient Reliable Evidence to RateToo little research to say either way.
Possibly Effective Pregnancy-related iron deficiency
Rating & evidence shown verbatim from Natural Medicines

Oral chlorella, which contains iron, can help to prevent iron deficiency and anemia in pregnancy.

Also studied for 14 conditions — evidence insufficient to rate
Insufficient Reliable Evidence To Rate Brain tumor
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral chlorella is beneficial in patients with glioma.

Insufficient Reliable Evidence To Rate Depression
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral chlorella is beneficial as an adjunct to conventional antidepressant therapy in patients with major depressive disorder.

Insufficient Reliable Evidence To Rate Dysmenorrhea
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral chlorella improves symptoms of dysmenorrhea.

Insufficient Reliable Evidence To Rate Exercise-induced respiratory infections
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral chlorella can prevent respiratory infections related to exercise.

Insufficient Reliable Evidence To Rate Fatigue
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral chlorella improves fatigue from exercise.

Insufficient Reliable Evidence To Rate Fibromyalgia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral chlorella improves symptoms of fibromyalgia.

Insufficient Reliable Evidence To Rate Halitosis
Rating & evidence shown verbatim from Natural Medicines

Although there is interest in using oral chlorella for halitosis, there is insufficient reliable information about the clinical effects of chlorella for this purpose.

Insufficient Reliable Evidence To Rate Hepatitis C
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral chlorella improves outcomes in patients with chronic hepatitis C infection.

Insufficient Reliable Evidence To Rate Hyperlipidemia
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral chlorella reduces lipid levels.

Insufficient Reliable Evidence To Rate Metabolic syndrome
Rating & evidence shown verbatim from Natural Medicines

Although there is interest in using oral chlorella for metabolic syndrome, there is insufficient reliable information about the clinical effects of chlorella for this condition.

Insufficient Reliable Evidence To Rate Nonalcoholic fatty liver disease (NAFLD)
Rating & evidence shown verbatim from Natural Medicines

Oral chlorella has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

Insufficient Reliable Evidence To Rate Peptic ulcers
Rating & evidence shown verbatim from Natural Medicines

Although there is interest in using oral chlorella for peptic ulcers, there is insufficient reliable information about the clinical effects of chlorella for this purpose.

Insufficient Reliable Evidence To Rate Pregnancy-induced hypertension
Rating & evidence shown verbatim from Natural Medicines

It is unclear if oral chlorella is beneficial for preventing pregnancy-induced hypertension.

Insufficient Reliable Evidence To Rate Ulcerative colitis
Rating & evidence shown verbatim from Natural Medicines

Although there is interest in using oral chlorella for ulcerative colitis, there is insufficient reliable information about the clinical effects of chlorella for this condition.

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

Chlorella is generally considered well tolerated for most healthy adults when taken short term. However, the quality of supplements can vary a lot. Because chlorella is grown in water, contaminated products may contain heavy metals, bacteria, or toxins, so choosing a reputable, tested brand is important.

People with autoimmune conditions should be cautious, since chlorella may affect the immune system. Those who are sensitive to iodine, mold, or who have a history of allergies should also be careful. People who are sensitive to vitamin K changes (for example, those on blood thinners) should talk to a pharmacist first.

Pregnancy and breastfeeding: There is not enough reliable safety information, so it is best to avoid chlorella during pregnancy and while breastfeeding unless your doctor specifically recommends it.

Always check with your pharmacist or doctor before starting chlorella, especially if you have a health condition or take other medicines.

Side effects

The most common side effects are digestive, especially when first starting. These can include nausea, gas, bloating, stomach cramps, and changes in bowel movements. Chlorophyll can turn the stool green, which is harmless.

Some people may have allergic reactions, including skin rash or, rarely, more serious breathing problems. There have also been reports of chlorella causing sensitivity to sunlight in some people.

Stop using chlorella and seek medical help if you have signs of a serious allergic reaction, such as swelling, trouble breathing, or a widespread rash.

Chlorella: Reported Adverse Effects

Documented safety reports on Chlorella from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

Orally, chlorella is generally well-tolerated.

Most Common Adverse Effects:

Orally: Allergic reactions, abdominal cramping, constipation, diarrhea, fatigue, flatus, nausea, photosensitivity, and stool discoloration.

Serious Adverse Effects (Rare):

Orally: Anaphylaxis.

Reports by condition
Asthma Immunologic

Allergic reactions, including asthma and anaphylaxis, have been reported in people taking chlorella and in those preparing chlorella tablets.

  1. Peirce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York, NY: William Morrow and Co., 1999.
  2. Ng TP, Tan WC, Lee YK. Occupational asthma in a pharmacist induced by chlorella, a unicellular algae preparation. Resp Med 1994;88:555-7.
  3. Ng, T. P., Tan, W. C., and Lee, Y. K. Occupational asthma in a pharmacist induced by Chlorella, a unicellular algae preparation. Respir.Med. 1994;88(7):555-557.
Constipation Gastrointestinal

Orally, chlorella can cause diarrhea, abdominal cramping, flatus, and nausea, especially during the first two weeks of treatment. In one clinical trial, one out of 42 patients reported nausea and one reported diarrhea. In another trial, taking chlorella tablets (Sun Chlorella A, Sun Chlorella Corp) and a chlorella extract (Wakasa Gold, Sun Chlorella Corp) resulted in transient worsening of constipation in 4 of 13 patients and transient mild diarrhea in 2 of 13 patients.

Green discoloration of the feces has also been reported, due to the chlorophyll content of chlorella.

  1. Merchant RE, Carmack CA, Wise CM. Nutritional supplementation with Chlorella pyrenoidosa for patients with fibromyalgia syndrome: a pilot study. Phytother Res 2000;14:167-73.
  2. Merchant RE, Rice CD, Young HF. Dietary Chlorella pyrenoidosa for patients with malignant glioma: effects on immunocompetence, quality of life, and survival. Phytother Res 1990;4:220-31.
  3. Azocar J, Diaz A. Efficacy and safety of chlorella supplementation in adults with chronic hepatitis C virus infection. World J Gastroenterol 2013;19(7):1085-90.
  4. Panahi Y, Badeli R, Karami GR, Badeli Z, Sahebkar A. A randomized controlled trial of 6-week Chlorella vulgaris supplementation in patients with major depressive disorder. Complement Ther Med 2015;23(4):598-602.
  5. Nakano S, Takekoshi H, Nakano M. Chlorella pyrenoidosa supplementation reduces the risk of anemia, proteinuria and edema in pregnant women. Plant Foods Hum Nutr 2010;65(1):25-30.
Fatigue Neurologic/CNS

Orally, manganese (Mn)-induced parkinsonism has been reported after long-term consumption of chlorella extract. In this case, a patient on maintenance hemodialysis reported gait disturbance, dysarthria, elevated serum and cerebrospinal fluid manganese levels, and abnormal magnetic resonance imaging (MRI) findings of the brain. The authors identified the condition as a rare case of Mn-induced parkinsonism, which may have been due to long-term ingestion of a chlorella extract containing 1.7 mg of Mn in the usual daily dose. The patient underwent edetic acid infusion therapy, which improved the MRI abnormalities and the other symptoms improved four months later.

In one study, fatigue was reported in 18 of 41 patients receiving chlorella 200 mg .

  1. Ohtake, T., Negishi, K., Okamoto, K., Oka, M., Maesato, K., Moriya, H., and Kobayashi, S. Manganese-induced Parkinsonism in a patient undergoing maintenance hemodialysis. Am J Kidney Dis 2005;46(4):749-753.
  2. Halperin SA, Smith B, Nolan C, et al. Safety and immunoenhancing effect of a Chlorella-derived dietary supplement in healthy adults undergoing influenza vaccination: randomized, double-blind, placebo-controlled trial. CMAJ 2003;169:111-7..
Myasthenia gravis Hematologic

Orally, chlorella has been linked to one case of thrombocytopenia; however, causality has not been determined. A 49-year-old female living in Turkey presented with thrombocytopenia (a platelet count of 27,000/mm3) after taking chlorella 1080 mg daily for 20 days. Platelet counts had been normal one month earlier, and returned to normal two weeks after discontinuing the chlorella supplement.

  1. Yavasoglu I, Turgutkaya A, Bolaman Z. Chlorella-induced thrombocytopenia. Sao Paulo Med J 2018;136(6):602-3.
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no official, standardized dose for chlorella. Studies have used a wide range of amounts, and products differ in strength and quality, so there is no one 'correct' dose.

The best approach is to follow the directions on the product label and start with a lower amount to see how your body reacts. Taking it with food may reduce stomach upset.

Because doses and product quality vary, talk with your pharmacist or doctor before starting, and choose a brand that is third-party tested for purity.

Pregnancy & Breastfeeding

Chlorella & Pregnancy

Possibly Safe

When used orally and appropriately in medicinal amounts for up to approximately 28 weeks. A commercially available chlorella supplement (Sun Chlorella A, Sun Chlorella Corp.) has been safely used in doses of 6 grams daily, starting during the 12-18th week of gestation and continuing until delivery.

  1. Nakano S, Takekoshi H, Nakano M. Chlorella pyrenoidosa supplementation reduces the risk of anemia, proteinuria and edema in pregnant women. Plant Foods Hum Nutr 2010;65(1):25-30.

Chlorella & Breastfeeding

Insufficient reliable information

Insufficient reliable information available; avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

© 2026 Therapeutic Research Center

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 13 references that drive our Chlorella monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Peirce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York, NY: William Morrow and Co., 1999.
  2. Ng TP, Tan WC, Lee YK. Occupational asthma in a pharmacist induced by chlorella, a unicellular algae preparation. Resp Med 1994;88:555-7. PubMed
  3. Jitsukawa K, Suizu R, Hidano A. Chlorella photosensitization. New phytophotodermatosis. Int J Dermatol 1984;23:263-8. PubMed
  4. Merchant RE, Carmack CA, Wise CM. Nutritional supplementation with Chlorella pyrenoidosa for patients with fibromyalgia syndrome: a pilot study. Phytother Res 2000;14:167-73.
  5. Merchant RE, Rice CD, Young HF. Dietary Chlorella pyrenoidosa for patients with malignant glioma: effects on immunocompetence, quality of life, and survival. Phytother Res 1990;4:220-31.
  6. Halperin SA, Smith B, Nolan C, et al. Safety and immunoenhancing effect of a Chlorella-derived dietary supplement in healthy adults undergoing influenza vaccination: randomized, double-blind, placebo-controlled trial. CMAJ 2003;169:111-7..
  7. Ohtake, T., Negishi, K., Okamoto, K., Oka, M., Maesato, K., Moriya, H., and Kobayashi, S. Manganese-induced Parkinsonism in a patient undergoing maintenance hemodialysis. Am J Kidney Dis 2005;46(4):749-753. PubMed
  8. Ng, T. P., Tan, W. C., and Lee, Y. K. Occupational asthma in a pharmacist induced by Chlorella, a unicellular algae preparation. Respir.Med. 1994;88(7):555-557. PubMed
  9. Ohkawa, S., Yoneda, Y., Ohsumi, Y., and Tabuchi, M. [Warfarin therapy and chlorella]. Rinsho Shinkeigaku 1995;35(7):806-807.
  10. Azocar J, Diaz A. Efficacy and safety of chlorella supplementation in adults with chronic hepatitis C virus infection. World J Gastroenterol 2013;19(7):1085-90. PubMed
  11. Panahi Y, Badeli R, Karami GR, Badeli Z, Sahebkar A. A randomized controlled trial of 6-week Chlorella vulgaris supplementation in patients with major depressive disorder. Complement Ther Med 2015;23(4):598-602. PubMed
  12. Nakano S, Takekoshi H, Nakano M. Chlorella pyrenoidosa supplementation reduces the risk of anemia, proteinuria and edema in pregnant women. Plant Foods Hum Nutr 2010;65(1):25-30. PubMed
  13. Yavasoglu I, Turgutkaya A, Bolaman Z. Chlorella-induced thrombocytopenia. Sao Paulo Med J 2018;136(6):602-3. PubMed
Keep reading

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Brand directory

Brands that make products with Chlorella

578 brands in our database make a supplement containing Chlorella.

Product directory

Supplement products with Chlorella

3,545 products in our database contain Chlorella. Open any to see its full ingredient list and every drug interaction we check.

Vegan Organic All in One Nutritional Shake Natural Unflavored by Natural Factors VegiDay Powder 12.7 Ounce(s) · 360 Gram(s) Off market View ingredients & interactions Vegan Organic All in One Shake & Go Decadent Chocolate by Natural Factors VegiDay Powder 15.9 Ounce(s) · 450 Gram(s) Off market View ingredients & interactions Vegan Organic All in One Shake & Go French Vanilla by Natural Factors VegiDay Powder 15.2 Ounce(s) · 430 Gram(s) Off market View ingredients & interactions Vegan Organic All in One Shake & Go Natural Unflavored by Natural Factors VegiDay Powder 12.7 Ounce(s) · 360 Gram(s) Off market View ingredients & interactions Vegan Protein Berrylicious by Natural Factors Powder 16 Oz(s) · 464 Gram(s) Off market View ingredients & interactions Vegan Protein Berrylicious by Natural Factors Powder 33 Oz(s) · 927 Gram(s) Off market View ingredients & interactions Vegan Protein Creamy Vanilla by Natural Factors Powder 17 Oz(s) · 486 Gram(s) Off market View ingredients & interactions Vegan Protein Decadent Chocolate by Natural Factors Powder 34 Oz(s) · 972 Gram(s) Off market View ingredients & interactions Vegan Protein Unflavored by Natural Factors Powder 13 Oz(s) · 371 Gram(s) Off market View ingredients & interactions Vegan Protein with Probiotics Natural Vanilla Flavor by Swanson GreenFoods Formulas Powder 25 Oz(s) · 1.56 lbs · 708 Gram(s) Off market View ingredients & interactions VGF 25+ For Men by Pro Grade Other (e.g. Tea Bag) 90 Caplet(s) Off market View ingredients & interactions Vibrance Energy Greens + Probiotics Citrus Cucumber by Vibrant Health Powder 240 Gram(s) · 8.47 oz. Off market View ingredients & interactions Vibrance Energy Greens + Probiotics Orange Pineapple by Vibrant Health Powder 240 Gram(s) · 8.47 oz. Off market View ingredients & interactions Vibrance Essential Daily Green Food Citrus Cucumber by Vibrant Health Powder 15 Single Serving Packet(s) · 130.6 Gram(s) · 4.6 oz. Off market View ingredients & interactions Vibrance Essential Daily Green Food Orange Pineapple by Vibrant Health Powder 255.21 Gram(s) · 9 oz. Off market View ingredients & interactions Vibrance Essential Daily Green Food Orange Pineapple by Vibrant Health Powder 8.507 Gram(s) · 0.3 oz. Off market View ingredients & interactions Vibrance Essential Daily Green Food Refreshing Citrus Cucumber by Vibrant Health Powder 8.707 Gram(s) · 0.307 oz. Off market View ingredients & interactions Vibrance Orange Pineapple by Vibrant Health Powder 15 Single Serve Packet(s) · 120 Gram(s) · 4.23 oz. Off market View ingredients & interactions Vision Health by Emerald Laboratories Capsule 60 Vegetable Capsule(s) Off market View ingredients & interactions Vital BodyGlo Delicious & Refreshing Fruit Flavor by Designed by Dean Powder 8.5 Oz(s) · 240 Gram(s) Off market View ingredients & interactions Vitality Greens by YES Youth Extension Solutions Powder 10.26 Ounce(s) · 291 Gram(s) Off market View ingredients & interactions Vitality Greens by HealthForce SuperFoods Powder 8 Oz(s) · 227 Gram(s) Off market View ingredients & interactions Vitality Greens by HealthForce SuperFoods Powder 20 Gram(s) · 0.71 Oz(s) Off market View ingredients & interactions Vitality SuperGreen by Body Ecology Powder 9.7 oz. · 279 Gram(s) Off market View ingredients & interactions
Pharmacist Counseling Corner

Chlorella: Common Questions

What is Chlorella used for, and does it work?
People use Chlorella for many reasons, but the evidence varies by use. According to the Natural Medicines database, there is at least some clinical evidence supporting Chlorella for Pregnancy-related iron deficiency. For most other uses it has been studied for, the evidence is currently insufficient to rate. See the graded list on this page, and always confirm with your pharmacist or doctor.
Does Chlorella interact with prescription medications?
Yes. We list 337 medications with a known interaction with Chlorella. Use the checker above to see how Chlorella interacts with a specific drug.
How are Chlorella interactions rated?
Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.
Is it safe to take Chlorella with my medications?
It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.
Where does this Chlorella interaction information come from?
Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.
What is Chlorella used for?
People commonly take Chlorella as a nutrient-rich supplement for general wellness, immune support, 'detox,' and heart health. While it is a good source of nutrients, strong proof that it treats specific health conditions is limited.
Is Chlorella safe to take every day?
Many healthy adults tolerate Chlorella well for short periods, but long-term safety is not well studied. Product quality varies, so choose a reputable, tested brand and check with your pharmacist if you plan to take it daily.
Can I take Chlorella while pregnant or breastfeeding?
There is not enough reliable safety information, so it is best to avoid Chlorella during pregnancy and breastfeeding unless your doctor specifically approves it.
Why does Chlorella turn my stool green?
Chlorella is rich in chlorophyll, the green pigment in plants, which can give stool a green color. This is harmless and not a cause for concern.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Products that contain Chlorella

A rotating sample of real supplements in our database that list Chlorella — open any to see its full ingredients and every drug interaction we check.

See all 3,545 products with Chlorella →
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