Is Acacia 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 breakfast. Do not take acacia fiber within 4 hours of levothyroxine. Monitor TSH levels more frequently when initiating or changing fiber supplementation.
Why this interaction occurs
Acacia fiber can bind to levothyroxine in the GI tract, reducing its bioavailability. Levothyroxine has a narrow therapeutic index and even modest reductions in absorption can lead to hypothyroidism or require dose adjustments. Soluble fibers are known to adsorb various medications, and thyroid hormones are particularly susceptible due to their physicochemical properties.
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 Acacia Fiber interactions → · All Levothyroxine interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.