Interactions on record — worth a quick check against your medications. Based on 1 of 2 ingredients. Check your meds →
Dietary supplement

Chlorella 1000 mg Ingredients & Drug Interactions

by NOW

Chlorella 1000 mg label
See full label image
Tablet Or Pill Category: Botanical
Most serious interaction: Moderate
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Chlorella 1000 mg against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Moderate

Chlorella 1000 mg is a dietary supplement by NOW with 2 active ingredients. Its ingredients are commonly taken for general nutrition and 'detox' support, immune support, liver and kidney support.Based on those ingredients, 337 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Chlorella. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

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Check Your Meds Against Chlorella 1000 mg by NOW

Ask about any prescription or over-the-counter medication and we check it for interactions with Chlorella 1000 mg by NOW — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Chlorella 1000 mg by NOW

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Jul 11, 2026

What’s inside

Full disclosure
Ingredient Transparency · database check
Full

Every active ingredient lists its own amount on the label.

Why this rating?
  • The label discloses an exact amount for 1 of its 1 active ingredient.
  • No proprietary blends here — you can verify the dose of every single component.

This product contains one active ingredient: chlorella, a single-celled freshwater green alga dosed at 1000 mg per tablet. The tablet also contains inactive ingredients (carboxymethyl cellulose, silicon dioxide, and magnesium stearate) that help bind and preserve the formula.

Does it work?

Moderate evidence
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed
Moderate

Some clinical evidence supports this product's ingredients for its stated purpose, but it isn't conclusive.

Why this rating?
  • The label markets this product for: General nutrition and nutrient support.
  • We looked for evidence on: Fatigue, Pregnancy-related iron deficiency, immune support, antioxidant support, whole food nutrition.
  • The strongest evidence on file: Chlorella is rated "Possibly Effective" for Pregnancy-related iron deficiency (Natural Medicines).
  • Also on file: Chlorella is rated "Insufficient Reliable Evidence To Rate" for Fatigue.

Chlorella is possibly effective for pregnancy-related iron deficiency based on available evidence. For other uses listed in our data — brain tumors, fatty liver disease, depression, and fatigue — the evidence isn't strong enough to establish whether it works.

If you're considering it for one of those conditions, talk with your pharmacist about what the current science supports.

The evidence, ingredient by ingredient Chlorella

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 1 of the 1 matched ingredient.
  • Pregnancy & breastfeeding safety ratings cover 1 of 1.
  • General safety write-ups exist for 1 of 1.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Chlorella is generally well tolerated in the short term, though product quality and purity vary widely from brand to brand. The most common side effects are allergic reactions, abdominal cramping, constipation, diarrhea, nausea, fatigue, gas, and changes in stool color.

These tend to appear early, especially in the first two weeks. Serious allergic reactions including anaphylaxis are rare but have been reported.

Because long-term safety data is limited, avoid use unless your doctor approves it. We have no pregnancy or breastfeeding safety information on file for chlorella, so talk with your pharmacist or doctor before taking it if you're pregnant or nursing.

Side effects, ingredient by ingredient Chlorella

Meds to double-check

Moderate interaction found
Known Interaction Concern · database check
Moderate identified

The most serious documented interaction for these ingredients is Moderate. Check your medications for a personalized result.

Why this rating?
  • 1 of the 1 matched ingredient can interact with medications — Chlorella.
  • The most serious interaction on file is rated Moderate.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs.
  • For scale: 337 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before you take Chlorella by NOW, check whether you're on warfarin (Coumadin) or any photosensitizing medications. Warfarin therapy can become less effective with chlorella because of its vitamin K content.

Photosensitizing drugs might have additive effects with chlorella's own photosensitizing potential. Use the interaction tool on this page to search your specific medications.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.

Chlorella might appeal to you if your doctor suggests it for pregnancy-related iron deficiency or if you're interested in its potential for liver or other uses — though evidence for most applications is still being studied. Be cautious if you take warfarin or medications that increase photosensitivity; check your exact medications with us first.

Also know that quality varies between brands. Talk with your pharmacist before starting, especially if you're pregnant, nursing, or on any regular medications.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Dec 21, 2024.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Chlorella 1000 mg, straight from the product label.

Brand NOW
Barcode (UPC) 733739026309
Net contents 60 Tablet(s)
Market status On market
Date entered into DSLD Dec 21, 2024
DSLD ID 313806
Product type Botanical
Supplement form Tablet Or Pill
Dietary claims / uses Nutrient, All Other
Intended target group(s) Vegan, Vegetarian, Adult (18 - 50 Years), Kosher, Halal, Gluten Free
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Chlorella 1000 mg by NOW, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
3 Tablet(s)
Maximum serving Sizes:
3 Tablet(s)
Servings per container
20
UPC/BARCODE
733739026309
IngredientAmount% DV
Calories10 Calorie(s)--
Total Carbohydrates1 Gram(s)1%
Protein2 Gram(s)--
Chlorella3 Gram(s)--

Other ingredients: Carboxymethyl Cellulose, Silicon Dioxide, Magnesium Stearate

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Suggested/Recommended/Usage/Directions

Suggested Use: Take 3 tablets daily.

Formula

NOW Chlorella delivers the natural nutrient profile found in genuine whole foods. Chlorella is a green single-celled microalgae that has naturally occurring chlorophyll, plus beta-carotene, mixed carotenoids, vitamin C, iron, and protein. The cell wall in this high quality chlorella has been broken down mechanically to aid digestibility.

Crescent H (Halal)

Naturally Occurring Chlorophyll & Beta-Carotene Broken Cell Wall Algae

Triangle K (Kosher)

Precautions

Caution: May cause GI discomfort in sensitive individuals.

Not manufactured with yeast, wheat, gluten, soy, corn, milk, egg, fish, shellfish, tree nut or sesame ingredients. Produced in a GMP facility that processes other ingredients containing these allergens.

Formulation

Natural color variation may occur in this product.

Super Green

Vegetarian/Vegan

Non-GMO Project Verified nongmoproject.org

Packaged and quality tested in the USA.

Not manufactured with yeast, wheat, gluten, soy, corn, milk, egg, fish, shellfish, tree nut or sesame ingredients.

Storage

Store in a cool, dry place after opening.

Seals/Symbols

Crescent H (Halal) GMP Quality Assured

Triangle K (Kosher)

Non-GMO Project Verified nongmoproject.org

FDA Statement of Identity

A Dietary Supplement

General Statements

Botanicals/Herbs Family owned since 1968.

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Chlorella 1000 mg by NOW label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Chlorella 1000 mg label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Chlorella 1000 mg by NOW

These are the 2 active ingredients this product is made of. Select any to open its full monograph.

Serving size3 Tablet(s) Dosage formTablet Or Pill Servings per container20 Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Protein

2 Gram(s) per serving

Chlorella

Interacts with
337 drugs
3 Gram(s) per serving

Chlorella is a nutrient-rich freshwater green algae taken as a supplement for general wellness, immune support, and 'detox.' Some small studies sugges...

Chlorella monograph & interactions

Other (inactive) ingredients: Carboxymethyl Cellulose, Silicon Dioxide, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

Chlorella 1000 mg by NOW Drug Interactions

Want to check YOUR meds against Chlorella 1000 mg?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
337Drugs
337 Moderate

Ingredients driving the most interactions

Chlorella 337

Individual Drug Interactions

The ingredients in Chlorella 1000 mg interact with 337 drugs. Click any drug to see the details.

1 of the 2 ingredients in Chlorella 1000 mg interact with drugs. Each result below shows which ingredient is responsible. Chlorella

Each ingredient & the kinds of drugs it affects

For each ingredient in Chlorella 1000 mg with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.

Chlorella2 drug types · 337 drugs

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
Chlorella full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Chlorella 1000 mg, from the product label.

NOW

See all NOW products
Name
NOW FOODS
Street Address
395 S. Glen Ellyn Rd.
City
Bloomingdale
State
IL
ZipCode
60108
Web Address
nowfoods.com
Pharmacist Counseling Corner

Chlorella 1000 mg by NOW: Common Questions

Does Chlorella 1000 mg by NOW interact with any medications?
Yes. Based on its ingredients, Chlorella 1000 mg has a known interaction with 337 medications. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Chlorella 1000 mg contains 2 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
What exactly is chlorella?
Chlorella is a single-celled freshwater green alga. Each tablet in this product contains 1000 mg of it. Quality and purity vary quite a bit between different brands and suppliers, so that's something to keep in mind when you're choosing a product.
Can I take this if I'm pregnant or breastfeeding?
We don't have safety information on file for chlorella during pregnancy or breastfeeding. Talk with your pharmacist or doctor before using it if you're pregnant, nursing, or planning to nurse. They can give you personalized advice based on your situation.
What side effects should I expect?
Most people tolerate it well, but common side effects include stomach cramping, nausea, diarrhea, constipation, gas, and fatigue — especially in the first two weeks. Allergic reactions and stool discoloration have been reported too. Serious allergic reactions like anaphylaxis are rare but possible.
Does chlorella actually work?
It's possibly effective for pregnancy-related iron deficiency based on current evidence. For brain tumors, fatty liver disease, depression, and fatigue, we don't have enough reliable evidence yet to say whether it works. Your pharmacist can help you figure out if it's right for what you're trying to address.
Why does product quality matter so much?
Chlorella's purity and quality can vary significantly from one brand or batch to another. That variation affects both how well it works and how safe it is, so it's worth paying attention to the manufacturer's quality standards.

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

Not sure if Chlorella 1000 mg is safe with your meds?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.

Chlorella 1000 mg label
Go deeper

The Full Monographs Behind Chlorella 1000 mg’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Chlorella

Interacts with 337 drugs

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, blo...

Read the full Chlorella monograph →
Sources

Sources & How We Checked

Chlorella 1000 mg's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 13 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Chlorella 13 references
  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

See these in context on the Chlorella monograph →

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

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