Is Thiamine (Vitamin B1) Safe with Furosemide?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Consider supplementing with thiamine 100 mg daily, especially in elderly patients, those with heart failure, or those with poor dietary intake. Report symptoms such as fatigue, confusion, leg swelling, or shortness of breath to your doctor promptly.
Why this interaction occurs
Furosemide significantly increases urinary thiamine excretion. Thiamine deficiency is particularly concerning in heart failure patients on long-term furosemide, as thiamine is essential for cardiac energy metabolism. Clinical studies have documented significantly lower thiamine levels in furosemide-treated patients, with thiamine supplementation shown to improve cardiac function in some trials.
Evidence
Evidence level: strong.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 274,011 reports mentioning Furosemide. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Furosemide + 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 Thiamine (Vitamin B1) interactions → · All Furosemide interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.