Drug & supplement interaction

Tannic Acid + Levothyroxine

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

No Known Interaction

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated July 2026 · Pair last verified Sep 13, 2026

The bottom line No known interaction

We found no known interaction between Tannic 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.

Know someone taking this? Share

Facebook Post Reddit Email

On this page

Interaction report

Tannic 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 Tannic 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 Tannic 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.

Tannic Acid safety at a glance

Tannic Acid overall Use caution Generally used topically in small amounts, but absorption through broken skin or large burns can harm the liver.

Pregnancy Possibly Unsafe When used topically on damaged or broken skin. There is insufficient reliable information available about the safety of tannic acid when used orally during preg... Read the full pregnancy detail

Breastfeeding Possibly Unsafe When used topically on damaged or broken skin. There is insufficient reliable information available about the safety of tannic acid when used orally during preg... 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 Tannic Acid? Ask Dr. Brian Staiger, PharmD, BCPS directly ›

What to actually watch for

No Interaction Found — But Data Suggests Tannic 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.

Vomiting / Nausea Additional detail
Tannic Acid
“Orally, large amounts of tannic acid can cause gastric irritation, nausea, and vomiting (11). Extensive use of tannins on burns or in enemas has been associated with fatal liver damage (11). However, this toxicity may be due to digallic acid, an impurity that is sometimes found in tannic acid (11).”

Tannic Acid · Natural Medicines adverse-effect record, reported in burns.
1 source cited

11. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
“Orally, large amounts of tannic acid can cause gastric irritation, nausea, and vomiting (11).”

Tannic Acid · Natural Medicines adverse-effect record, reported in nausea and vomiting.
1 source cited

11. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
Levothyroxine

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

Reported for Tannic Acid but not commonly for Levothyroxine: stomach upset and liver problems.

Effects for Levothyroxine come from the ADVERSE REACTIONS section of its FDA label; effects for Tannic 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

Tannic Acid in Pregnancy & Breastfeeding

Pregnancy And Lactation Possibly Unsafe

When used topically on damaged or broken skin. There is insufficient reliable information available about the safety of tannic acid when used orally during pregnancy and lactation; avoid using 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 — Tannic 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 — Tannic 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 Tannic 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 Tannic 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 Tannic 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 Tannic 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

How much people look this up

Where Tannic 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 Tannic Acid

Steady interest

#1,046 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 Tannic Acid reference on this page ↓
Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Tannic 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 Dr. Brian Staiger, PharmD, BCPS.

Supplement

About Tannic Acid

What is Tannic Acid?

Minor skin irritation and weeping rashes
Sore throat and mouth sores
Minor burns and blisters
Astringent for skin
Hemorrhoids

Tannic acid is a plant-derived astringent used mostly on the skin and in the mouth to dry out and tighten tissue. There is some traditional and topical use, but high-quality evidence for most uses is limited, and it can be harmful if too much is absorbed, especially on broken skin or burns.

Tannins extracted from plant sources such as oak galls, bark, and certain seeds and leaves · Topical powders and solutions, throat lozenges, gargles, suppositories, and some over-the-counter skin products

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

Tannic Acid: dosing

There is no well-established standard dose of tannic acid for supplement use. The amount varies widely depending on the product and how it is used (for example, a skin solution versus a lozenge).The safest approach is to follow the directions on the product label and not apply it to large areas of broken or burned skin.

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

Read the full Tannic 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 & Tannic Acid

Browse every other medication we’ve checked against Tannic 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 Tannic 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 Tannic Acid list.

See the full Tannic Acid interactions page

See every supplement checked against Levothyroxine, ranked by severity

Evidence & sources

Tannic Acid References

The 8 references that drive our Tannic 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.

Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
Covington TR, et al. Handbook of Nonprescription Drugs. 11th ed. Washington, DC: American Pharmaceutical Association, 1996.
Laslett, L. L., Quinn, S. J., Darian-Smith, E., Kwok, M., Fedorova, T., Korner, H., Steels, E., March, L., and Jones, G. Treatment with 4Jointz reduces knee pain over 12 weeks of treatment in patients with clinical knee osteoarthritis: a randomised contr
Smith DB, Jacobson BH. Effect of a blend of comfrey root extract (Symphytum officinale L.) and tannic acid creams in the treatment of osteoarthritis of the knee: randomized, placebo-controlled, double-blind, multiclinical trials. J Chiropr Med. 2011;10(3) PubMed
Goh CL, Yoyong K. A comparison of topical tannic acid versus iontophoresis in the medical treatment of palmar hyperhidrosis. Singapore Med J. 1996;37(5):466-8.
Ko&lstrok;odziej M, Bebenek D, Konarska Z, Szajewska H. Gelatine tannate in the management of acute gastroenteritis in children: a randomised controlled trial. BMJ Open. 2018;8(5):e020205. PubMed
Mennini M, Tolone C, Frassanito A, Midulla F, Cucchiara S, Aloi M. Gelatin tannate for acute childhood gastroenteritis: a randomized, single-blind controlled trial. Paediatr Drugs. 2017 Apr;19(2):131-137. PubMed

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 Tannic Acid and Levothyroxine Together: Common Questions

Is it safe to take Tannic Acid with Levothyroxine?

We do not list a known interaction between Tannic 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 Tannic 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 Tannic 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 Tannic 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 — Tannic 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

Tannic 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 8 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Levothyroxine and Tannic Acid?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.