Drug & supplement interaction

Phytase + 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 Phytase 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

Phytase 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 Phytase 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 Phytase 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.

Phytase safety at a glance

Phytase overall Use caution Generally considered low-risk in foods, but human supplement data are limited.
Pregnancy Not established There is not enough reliable safety information, so avoid unless advised by your doctor.
Breastfeeding Not established Safety while breastfeeding has not been well studied; use caution and check with a doctor.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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

No Interaction Found — But Data Suggests Phytase 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. 4 of them are worth acting on rather than waiting out — marked below.

  • Wheezing / Chest pain / Shortness of breath / An allergic reaction Worth acting on Additional detail

    Phytase

    “There are numerous reports of immunologic responses to airborne powdered phytase in the animal-feed industry. Examples of reactions include allergic occupational asthma and hypersensitivity pneumonitis. In one case report of a 43-year-old male, hypersensitivity pneumonitis related to phytase was diagnosed following a 6-month history of coughing, shortness of breath, fever, and dyspnea.”

    Phytase · Natural Medicines adverse-effect record, reported in allergic rhinitis (hay fever).

    4 sources cited
    1. 101901. Lei XG, Weaver JD, Mullaney E, Ullah AH, Azain MJ. Phytase, a new life for an "old" enzyme. Annu Rev Anim Biosci. 2013;1:283-309. PubMed
    2. 101908. van Heemst RC, Sander I, Rooyackers J, et al. Hypersensitivity pneumonitis caused by occupational exposure to phytase. Eur Respir J. 2009;33(6):1507-9. PubMed
    3. 101909. Baur X, Melching-Kollmuss S, Koops F, Strassburger K, Zober A. IgE-mediated allergy to phytase -- a new animal feed additive. Allergy. 2002;57(10):943-5. PubMed
    4. 101910. Doekes G, Kamminga N, Helwegen L, Heederik D. Occupational IgE sensitisation to phytase, a phosphatase derived from Aspergillus niger. Occup Environ Med. 1999;56(7):454-9. PubMed

    Levothyroxine

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

  • Fever Additional detail

    Phytase

    Recorded for Phytase in the same Natural Medicines adverse-effect record shown under Wheezing / Chest pain / Shortness of breath / An allergic reaction above.

    Levothyroxine

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

Reported for Phytase but not commonly for Levothyroxine: cough and a stuffy or runny nose.

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

How to take them

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

At least one FDA label for a product containing Levothyroxine says to take it on an empty stomach. Most supplements — Phytase 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 Phytase 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 Phytase 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 Phytase 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 Phytase 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 Phytase as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,063 real supplement products containing Phytase, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Phytase. Even though Phytase 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 Phytase 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 Phytase
Top 25%

#239 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 Phytase reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Phytase 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 Phytase

What is Phytase?

  • Improving mineral absorption
  • Breaking down phytic acid (phytate) in grains and legumes
  • Supporting digestion of plant-based foods
  • Reducing 'anti-nutrient' effects of high-phytate diets

Phytase is an enzyme that breaks down phytic acid (phytate) found in grains, beans, nuts, and seeds, which can free up minerals like iron, zinc, and calcium for absorption. It is widely used in animal feed and food processing, but human supplement research is limited, so talk to a pharmacist or doctor before using it.

Enzyme (often derived from fungi, bacteria, or plants such as wheat and rice bran) · Capsules, tablets, powder, and as an added ingredient in some digestive enzyme blends

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

Phytase: dosing

There is no established standard dose of phytase for people. Phytase activity is often measured in special enzyme units (sometimes listed as "FTU" or "phytase units") rather than simple milligrams, and products vary widely.Because of this, the best approach is to follow the directions on the product label and not exceed them.

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

Read the full Phytase 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 & Phytase

Browse every other medication we’ve checked against Phytase — 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 Phytase 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 Phytase list.

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

Phytase References

The 7 references that drive our Phytase 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. Lei XG, Weaver JD, Mullaney E, Ullah AH, Azain MJ. Phytase, a new life for an "old" enzyme. Annu Rev Anim Biosci. 2013;1:283-309. PubMed
  2. Smuts CM, Matsungo TM, Malan L, et al. Effect of small-quantity lipid-based nutrient supplements on growth, psychomotor development, iron status, and morbidity among 6- to 12-mo-old infants in South Africa: a randomized controlled trial. Am J Clin Nutr. 2 PubMed
  3. van Heemst RC, Sander I, Rooyackers J, et al. Hypersensitivity pneumonitis caused by occupational exposure to phytase. Eur Respir J. 2009;33(6):1507-9. PubMed
  4. Baur X, Melching-Kollmuss S, Koops F, Strassburger K, Zober A. IgE-mediated allergy to phytase -- a new animal feed additive. Allergy. 2002;57(10):943-5. PubMed
  5. Doekes G, Kamminga N, Helwegen L, Heederik D. Occupational IgE sensitisation to phytase, a phosphatase derived from Aspergillus niger. Occup Environ Med. 1999;56(7):454-9. PubMed
  6. Brnic M, Hurrell RF, Songré-Ouattara LT, et al. Effect of phytase on zinc absorption from a millet-based porridge fed to young Burkinabe children. Eur J Clin Nutr. 2017;71(1):137-141. PubMed
  7. Koshy JC, Sharabi SE, Feldman EM, Hollier LH Jr, Patrinely JR, Soparkar CN. Effect of dietary zinc and phytase supplementation on botulinum toxin treatments. J Drugs Dermatol. 2012;11(4):507-12.

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 Phytase and Levothyroxine Together: Common Questions

Is it safe to take Phytase with Levothyroxine?
We do not list a known interaction between Phytase 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 Phytase and Levothyroxine have any of the same side effects?
Yes — our sources link each of them separately to 5 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 Phytase 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 Phytase 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 — Phytase 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

Phytase 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 7 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Levothyroxine and Phytase?

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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.