Is Psyllium Husk / Dietary Fiber Safe with Levothyroxine?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Take levothyroxine on an empty stomach 30–60 minutes before consuming fiber supplements or high-fiber foods. Do not take psyllium husk, glucomannan, or other fiber supplements at the same time as levothyroxine. Separate by at least 2–4 hours.
Why this interaction occurs
Soluble fiber supplements such as psyllium husk bind bile acids and can also bind levothyroxine within the gut lumen, reducing its absorption through enterohepatic circulation interference. High-fiber diets have been associated with increased levothyroxine dose requirements. This is particularly relevant for patients who take fiber supplements for cholesterol or bowel health and may not realize the timing impact on their thyroid medication efficacy.
Evidence
Evidence level: moderate.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 302,514 reports mentioning Levothyroxine. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Levothyroxine + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All Psyllium Husk / Dietary Fiber interactions → · All Levothyroxine interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.