Drug & supplement interaction

Citric Acid + Levothyroxine

Levothyroxine brand names: Euthyrox, Levothroid, Unithroid, Synthroid, Levoxyl, and others.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Citric Acid and Levothyroxine in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the label for Levothyroxine states a food rule worth keeping to, and the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Citric Acid and Levothyroxine

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Levothyroxine and Citric Acid in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

Worth understanding: our licensed dataset holds no drug-interaction record for Citric Acid at all — not against Levothyroxine, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Citric Acid safety at a glance

Citric Acid overall Generally safe Generally recognized as safe in the small amounts found in foods and most supplements.
Pregnancy Likely Safe When citric acid is used orally in the amounts commonly found in foods. There is insufficient reliable information available about the safety of citric acid whe... Read the full pregnancy detail
Breastfeeding Likely Safe When citric acid is used orally in the amounts commonly found in foods. There is insufficient reliable information available about the safety of citric acid whe... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Levothyroxine and Citric Acid? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

No Interaction Found — But Data Suggests Citric Acid and Levothyroxine May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Itching Additional detail

    Citric Acid

    “Topically, citric acid seems to be well tolerated when used as part of formulations containing the alpha hydroxy acids glycolic acid and lactic acid in concentrations at or below 10% and applied to the face. In general, products should be tested on a small area of skin before applying it to a larger area.

    Alpha hydroxy acids like citric acid can increase sensitivity to the sun and ultraviolet (UV) light.”

    Citric Acid · Natural Medicines adverse-effect record, reported in burns.

    6 sources cited
    1. 106612. US Food and Drug Administration (FDA). Cosmetic Ingredients: Alpha Hydroxy Acids. August 2020. Available at: https://www.fda.gov/cosmetics/cosmetic-ingredients/alpha-hydroxy-acids. Accessed on October 19, 2021.
    2. 6080. Kurtzweil P. Alpha-hydroxy acids for skin care: Smooth sailing or rough seas? FDA 1999. Available at: /www.fda.gov/fdac/features/1998/298_ahas.html (Accessed 18 August 2000). DOI
    3. 10101. Erbagci Z, Akcali C. Biweekly serial glycolic acid peels vs. long-term daily use of topical low-strength glycolic acid in the treatment of atrophic acne scars. Int J Dermatol 2000;39:789-94.. PubMed
    4. 92209. Baumann LS, Oresajo C, Yatskayer M, Dahl A, Figueras K. Comparison of clindamycin 1% and benzoyl peroxide 5% gel to a novel composition containing salicylic acid, capryloyl salicylic acid, HEPES, glycolic acid, citric acid, and dioic acid in the treatment
    5. 92210. Emtestam L, Svensson Å, Rensfeldt K. Treatment of seborrhoeic dermatitis of the scalp with a topical solution of urea, lactic acid, and propylene glycol (K301): results of two double-blind, randomised, placebo-controlled studies. Mycoses. 2012 Sep;55(5):3 PubMed
    6. 92214. Kaminaka C, Uede M, Matsunaka H, Furukawa F, Yamomoto Y. Clinical evaluation of glycolic acid chemical peeling in patients with acne vulgaris: a randomized, double-blind, placebo-controlled, split-face comparative study. Dermatol Surg. 2014 Mar;40(3):314- PubMed

    Levothyroxine

    Listed in the ADVERSE REACTIONS section of the FDA label for Levothyroxine. Read the label on DailyMed ›

  • A skin rash Additional detail

    Citric Acid

    Recorded for Citric Acid in the same Natural Medicines adverse-effect record shown under Itching above.

    Levothyroxine

    Listed in the ADVERSE REACTIONS section of the FDA label for Levothyroxine. Read the label on DailyMed ›

Reported for Citric Acid but not commonly for Levothyroxine: sun sensitivity, numbness or tingling, swelling and bleeding or bruising.

Effects for Levothyroxine come from the ADVERSE REACTIONS section of its FDA label; effects for Citric Acid come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Citric Acid in Pregnancy & Breastfeeding

Pregnancy And Lactation Likely Safe

When citric acid is used orally in the amounts commonly found in foods. There is insufficient reliable information available about the safety of citric acid when used orally in larger amounts during pregnancy or lactation; avoid amounts greater than those found in foods.

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

How to take them

Some Levothyroxine Products Have a Food Rule — Citric Acid Should Not Break It

At least one FDA label for a product containing Levothyroxine says to take it on an empty stomach. Most supplements — Citric Acid included — are taken with a meal, so the easy mistake is swallowing both together at breakfast. Where that rule applies, keep Levothyroxine on its own and move Citric Acid to a meal later in the day.

This may not be true of your version. Food instructions belong to the product, not the ingredient: two Levothyroxine products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.

A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.

From our Q&A

Questions About Citric Acid or Levothyroxine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Citric Acid or Levothyroxine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Levothyroxine

This page covers Citric Acid only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levothyroxine page lists 50 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Tiratricol (major), Acetyl-l-carnitine (moderate), Alpha-lipoic Acid (moderate) and Ascophyllum Nodosum (moderate).

By severity: 2 major · 39 moderate · 9 minor.

From our pharmacist’s overview on the Levothyroxine page

“Levothyroxine replaces a hormone your body measures in tiny amounts, so small shifts in its blood level show up in how you feel, and I treat this list with genuine care. Nearly everything on it does one of two things: blocks the pill from being absorbed in the gut, the way everyday minerals like calcium do by binding it into complexes,…”

Reviewed by 2 · Jul 18, 2026

Open the Levothyroxine interaction page

One more smart check

Taking Citric Acid as Part of a Dietary Supplement Product? Check It for Interactions

We hold 331 real supplement products containing Citric Acid, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Citric Acid. Even though Citric Acid itself has no known interaction with Levothyroxine, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Citric Acid and Levothyroxine Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Citric Acid
Top 25%

#274 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Levothyroxine
Top 10

#2 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Citric Acid reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Citric Acid and Levothyroxine records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Citric Acid

What is Citric Acid?

  • Food and drink flavoring or sourness
  • Preservative and acidity adjuster
  • Kidney stone prevention (as citrate salts)
  • Cleaning and descaling (non-medical)
  • Effervescent supplement and antacid blends

Citric acid is a natural acid found in citrus fruits and is widely used as a safe food additive, flavoring, and preservative. In medicine, citrate forms (like potassium or sodium citrate) are used to help prevent certain kidney stones and to make urine less acidic. For most people the small amounts in foods and supplements are safe, but concentrated products can irritate the mouth, stomach, and skin.

Naturally found in citrus fruits; commercially made by fermentation · Powder, crystals, liquid, effervescent tablets, and as an ingredient in foods, drinks, and supplements

An interaction check asks whether these two react with each other — it does not ask whether Citric Acid is a good idea for someone in your situation. Here is what our Citric Acid record says about it on its own.

Citric Acid: dosing

There is no standard supplement dose of plain citric acid, because it is mainly used as a food ingredient rather than a treatment. Amounts used in foods and drinks are small and considered safe.For medicinal citrate products (such as potassium citrate or sodium citrate used for kidney stones or urine alkalinization), dosing is individualized and should be set by a doctor, often based on lab tests.

From our Citric Acid monograph — the full record covers uses, side effects and every documented interaction.

Read the full Citric Acid monograph & all interactions
Medication

About Levothyroxine

What Is Levothyroxine Used For?

Brand names: Euthyrox, Levothroid, Unithroid, Synthroid, Levoxyl, Levo-T, Eltroxin, Estre, Levothyroxine, Novothyrox, Levolet

Levothyroxine replaces or supplements the thyroid hormone your body isn't making enough of. It's used for hypothyroidism — an underactive thyroid — in adults, children, and even newborns, whether the cause is the thyroid gland itself, the pituitary gland, or the hypothalamus in the brain.

It's also used alongside surgery and radioiodine treatment in people with certain types of thyroid cancer, to help suppress the hormone that can stimulate cancer growth. It is not meant for weight loss, treating benign thyroid nodules in people who have enough iodine, or for hypothyroidism during recovery from a temporary condition called subacute thyroiditis.

See full Levothyroxine drug information
Keep checking

Other Drugs & Citric Acid

Browse every other medication we’ve checked against Citric Acid — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

We also checked Citric Acid against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Citric Acid list.

See the full Citric Acid interactions page
See every supplement checked against Levothyroxine, ranked by severity
Evidence & sources

Citric Acid References

The 10 references that drive our Citric Acid 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. Kurtzweil P. Alpha-hydroxy acids for skin care: Smooth sailing or rough seas? FDA 1999. Available at: /www.fda.gov/fdac/features/1998/298_ahas.html (Accessed 18 August 2000). DOI
  2. Erbagci Z, Akcali C. Biweekly serial glycolic acid peels vs. long-term daily use of topical low-strength glycolic acid in the treatment of atrophic acne scars. Int J Dermatol 2000;39:789-94.. PubMed
  3. Ghadishah D, Gorchynski J. Airway compromise after routine alpha-hydroxy facial peel administration. J Emerg Med 2002;22:353-5.. PubMed
  4. Baumann LS, Oresajo C, Yatskayer M, Dahl A, Figueras K. Comparison of clindamycin 1% and benzoyl peroxide 5% gel to a novel composition containing salicylic acid, capryloyl salicylic acid, HEPES, glycolic acid, citric acid, and dioic acid in the treatment
  5. Emtestam L, Svensson Å, Rensfeldt K. Treatment of seborrhoeic dermatitis of the scalp with a topical solution of urea, lactic acid, and propylene glycol (K301): results of two double-blind, randomised, placebo-controlled studies. Mycoses. 2012 Sep;55(5):3 PubMed
  6. Kaminaka C, Uede M, Matsunaka H, Furukawa F, Yamomoto Y. Clinical evaluation of glycolic acid chemical peeling in patients with acne vulgaris: a randomized, double-blind, placebo-controlled, split-face comparative study. Dermatol Surg. 2014 Mar;40(3):314- PubMed
  7. Köse O, Özmen I, Arca E. An open, comparative study of 10% potassium hydroxide solution versus salicylic and lactic acid combination in the treatment of molluscum contagiosum in children. J Dermatolog Treat. 2013 Aug;24(4):300-4. PubMed
  8. Vachiramon V, Sahawatwong S, Sirithanabadeekul P. Treatment of melasma in men with low-fluence Q-switched neodymium-doped yttrium-aluminum-garnet laser versus combined laser and glycolic acid peeling. Dermatol Surg. 2015 Apr;41(4):457-65. PubMed
  9. US Food and Drug Administration (FDA). Cosmetic Ingredients: Alpha Hydroxy Acids. August 2020. Available at: https://www.fda.gov/cosmetics/cosmetic-ingredients/alpha-hydroxy-acids. Accessed on October 19, 2021.
  10. Ormerod AD, van Voorst Vader PC, Majewski S, Vanscheidt W, Benjamin N, van der Meijden W. Evaluation of the efficacy, safety, and tolerability of 3 dose regimens of topical sodium nitrite with citric acid in patients with anogenital warts: A randomized cl DOI

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Citric Acid and Levothyroxine Together: Common Questions

Is it safe to take Citric Acid with Levothyroxine?
We do not list a known interaction between Citric Acid and Levothyroxine. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Citric Acid and Levothyroxine have any of the same side effects?
Yes — our sources link each of them separately to 2 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Should I take Citric Acid and Levothyroxine at the same time of day?
At least one FDA label for a product containing Levothyroxine says to take it on an empty stomach, and supplements are usually taken with a meal — so taking them together at breakfast is the easy mistake. Where that applies, keep Levothyroxine on its own and move Citric Acid to a meal later in the day. Food instructions belong to the product rather than the ingredient, so check the directions on your own box. This is about absorption, not an interaction.
Does Levothyroxine interact with any supplements?
Yes. Levothyroxine has documented interactions with 50 supplements in our database — Citric Acid is not one of them. The Levothyroxine interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Citric Acid monograph Uses, safety profile, and every drug interaction in one place Levothyroxine drug information The full plain-English guide to this medication Levothyroxine supplement interactions Every supplement checked against Levothyroxine, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 10 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Levothyroxine and Citric Acid?

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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.