Long-term use (more than 6 months) of loop diuretics might lead to magnesium deficiency.^1,2,3 In turn, magnesium depletion can increase loss of potassium.⁴

Since magnesium deficiency is common anyway, taking a magnesium supplement at standard U.S. Dietary Reference Intake (formerly known as the Recommended Dietary Allowance) levels might make sense.

Evidence suggests that loop diuretics interfere with the body’s metabolism of vitamin B ₁ (thiamin).^5,9,10

This effect may cause adverse consequences in one group of individuals who commonly take loop diuretics: people with heart failure. The heart depends on B ₁ for proper function; therefore, this finding suggests that taking a B ₁ supplement may be advisable. In fact, preliminary evidence suggests that thiamin supplementation does indeed improve heart function in individuals with congestive heart failure (CHF).^6,7,11

Licorice, too, affects potassium, and the combination of licorice and loop diuretics might cause unexpectedly rapid potassium loss.⁸ However, the special form of licorice known as DGL (deglycyrrhizinated licorice) should not affect potassium levels.