Thiamin (vitamin B1) deficiency appears to be common in people with congestive heart failure—especially those taking diuretics such as furosemide (Lasix).
Several studies suggest this deficiency may worsen cardiac function and that supplementation could offer benefit.

Thiamin Deficiency in CHF Patients

A study published in the Journal of the American College of Cardiology (2006;47:354–61) compared 100 hospitalized patients with congestive heart failure (CHF) to 50 healthy controls.

  • 33% of CHF patients were thiamin deficient

  • Only 12% of healthy controls were deficient

Diuretics and Thiamin Loss

Furosemide, a commonly prescribed diuretic for CHF, increases urinary loss of thiamin.
In The American Journal of Medicine (1991;151–155), researchers evaluated 23 CHF patients taking furosemide:

  • 21 of 23 (91%) showed laboratory signs of thiamin deficiency

  • Only 2 of 16 controls were deficient

These findings mirror the 2006 JACC results, reinforcing that thiamin deficiency is significantly more common in CHF patients—especially those using diuretics.

Why This Matters: Thiamin and Heart Function

Severe thiamin deficiency leads to wet beriberi, a condition marked by:

  • Cardiomegaly (enlarged heart)

  • Congestive heart failure

  • Fluid retention

Even mild deficiency may impair cardiac energy metabolism.

Thiamin Supplementation May Improve Heart Function

In a double-blind study published in The American Journal of Medicine (May 1995;98:485–490), 30 patients with severe CHF taking furosemide received either:

  • IV thiamin (200 mg/day), or

  • Placebo

Of the 27 participants who completed the 7-week trial, the thiamin group experienced a 22% improvement in left ventricular ejection fraction, while the placebo group did not.

The authors concluded that thiamin supplementation may be a beneficial adjunct to standard CHF therapy.