Drug & supplement interaction

Cassava + Levothyroxine Sodium

Levothyroxine Sodium brand names: Tirosint-Sol, Thyquidity, Ermez.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Cassava has a moderate interaction with Levothyroxine Sodium. Evidence from human and animal research suggests that cassava root has marked antithyroid effects, particularly if poorly processed or if consumed as part of a protein-deficient diet.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Cassava and Levothyroxine Sodium

Here is the interaction we found between these two, with the evidence behind it.

Moderate

THYROID HORMONE

Why this applies to Levothyroxine Sodium

Levothyroxine Sodium falls under THYROID HORMONE — the group Cassava interacts with.

Evidence from human and animal research suggests that cassava root has marked antithyroid effects, particularly if poorly processed or if consumed as part of a protein-deficient diet. Also, clinical research shows that consuming boiled cassava leaves 200 grams twice daily for 9 days significantly reduces levels of the thyroid hormones triiodothyronine and thyroxine. Theoretically, cassava may alter thyroid function, reduce thyroid hormone levels, and interfere with thyroid hormone-replacement therapy.
Severity Moderate Likelihood Possible Evidence D

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.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist for you. Levothyroxine is the replacement thyroid hormone you take because your own thyroid isn't making enough. The concern with cassava is that it seems to have antithyroid activity, meaning it can push your thyroid hormone levels down. So if you're taking cassava in concentrated supplement amounts (or eating a lot of poorly processed cassava on a low-protein diet), it could work against your levothyroxine and leave you under-treated.

If that happened, you might notice the symptoms you take this medicine to avoid: feeling tired, cold, sluggish, constipated, or some weight gain. I'll be honest, this is mostly a theoretical worry based on how cassava behaves, not a well-proven clash. Normal food amounts are unlikely to matter much. Still, don't change your levothyroxine on your own. Just loop in your pharmacist or doctor before using cassava products, and keep up with your routine thyroid blood work.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Akindahunsi AA, Grissom FE, Adewusi SR, et al. Parameters of thyroid function in the endemic goitre of Akungba and Oke-Agbe villages of Akoko area of southwestern Nigeria. Afr J Med Med Sci 1998;27(3-4):239-42.
  2. Osman BA, Ng ML, Bakar AA, Khalid BA. The effect of cassava leave intake on thyroid hormone and urinary iodine. East Afr Med J 1993;70(5):314-5.
  3. Gaitan E, Cooksey RC, Legan J, et al. Antithyroid effects in vivo and in vitro of babassu and mandioca: a staple food in goiter areas of Brazil. Eur J Endocrinol 1994;131(2):138-44. PubMed
  4. Geelhoed GW. Metabolic maladaptation: individual and social consequences of medical intervention in correcting endemic hypothyroidism. Nutrition 1999;15(11-12):908-32. DOI
  5. Biassoni P, Ravera G, Bertocchi J, et al. Influence of dietary habits on thyroid status of a nomadic people, the Bororo shepherds, roaming a central African region affected by severe iodine deficiency. Eur J Endocrinol 1998;138(6):681-5. PubMed
  6. Delange F. The disorders induced by iodine deficiency. Thyroid 1994;4(1):107-28. PubMed
  7. Delange F. [The role of goitrogenic factors distinct from iodine deficiency in the etiology of goiter]. Ann Endocrinol (Paris) 1988;49(4-5):302-5.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction 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.
  • PossibleInteraction 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.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Cassava Also Interacts With Other Medications

Cassava has 15 moderate known drug interactions in our database — the Levothyroxine Sodium one above is one of them. If you take anything else, check it against the full list below.

Moderate 15 No known interaction 2,815 (incl. Levothyroxine Sodium)
Taking anything else?

Check Another of Your Medications Against Cassava

Covers the 2,830 medications we’ve checked against Cassava. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Levothyroxine Sodium

This page covers Cassava only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levothyroxine Sodium 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).

Open the Levothyroxine Sodium interaction page

One more smart check

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

We hold 35 real supplement products containing Cassava, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Cassava. Your product may carry other ingredients that interact with Levothyroxine Sodium too, on top of Cassava — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Cassava and Levothyroxine Sodium 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 Cassava
Steady interest

#1,213 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Levothyroxine Sodium
Top 5%

#126 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.

Supplement

About Cassava

What is Cassava?

Cassava
  • Dietary staple/source of carbohydrates
  • Fertility aid (to conceive twins)
  • Digestive support
  • General energy
  • Gluten-free flour alternative

Cassava is a starchy root vegetable that feeds millions of people worldwide, but it must be properly cooked or processed because the raw plant contains compounds that release cyanide. As a supplement, it is marketed for fertility and twin conception, but there is no good scientific evidence to support these claims. Always prepare cassava correctly and talk to your pharmacist or doctor before using cassava products for health reasons.

Read the full Cassava monograph & all interactions
Keep checking

Other Drugs & Cassava

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

0Major
15Moderate
0Minor
2,814No known interaction
15 Moderate 2,814 No interaction
Moderate

15 interactions

No interaction 2,814 drugs checked — show the list

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

Showing the 60 most looked-up of 2,814 medications checked with no known interaction — see the full Cassava list.

See the full Cassava interactions page
See every supplement checked against Levothyroxine Sodium, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

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

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

Keep exploring
Cassava monograph › Uses, safety, and every drug interaction in one place Levothyroxine Sodium supplement interactions › Every supplement checked against Levothyroxine Sodium, 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 Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Cassava and Levothyroxine Sodium Together: Common Questions

Can you take Cassava with Levothyroxine Sodium?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Cassava and Levothyroxine Sodium interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Levothyroxine Sodium and Cassava?

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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.