Losartan does not appear to deplete magnesium in any clinically meaningful way. While the drug technically increases urinary excretion of magnesium along with several other minerals, clinical studies show that serum magnesium levels remain stable during losartan treatment. The confusion likely stems from the fact that losartan is frequently prescribed alongside a diuretic called hydrochlorothiazide (HCTZ), and that combination does carry a real risk of magnesium depletion.
What Losartan Does to Minerals
Losartan works by blocking a hormone receptor involved in blood pressure regulation. As a side effect of how it influences the kidneys, it increases the urinary excretion of several minerals: sodium, potassium, chloride, magnesium, calcium, and phosphate. On paper, that sounds like it should lower your magnesium levels over time.
But a prospective study in hypertensive patients found that serum, urinary, and cellular magnesium levels were not significantly affected by losartan treatment. The body appears to compensate well enough that the extra magnesium lost in urine doesn’t translate into a measurable drop in blood levels. Interestingly, the same study found that losartan did cause a significant increase in zinc excretion and led to zinc deficiency, so the drug’s effects on different minerals aren’t uniform.
The Real Culprit: Hydrochlorothiazide
Many people taking losartan are actually prescribed a combination pill that includes hydrochlorothiazide, a thiazide diuretic. This combination is sold under the brand name Hyzaar, among others. Thiazide diuretics are well-known magnesium depleters, and the FDA prescribing label for the losartan/HCTZ combination specifically warns that it “can cause hypokalemia, hyponatremia and hypomagnesemia.” The label also notes that low magnesium can make low potassium harder to correct, even with potassium supplements.
If you’re taking a combination pill rather than losartan alone, that’s an important distinction. Check your prescription: if it says “losartan/hydrochlorothiazide” or “Hyzaar,” the diuretic component is the one that puts you at risk for magnesium loss. Your prescriber will typically monitor your electrolytes periodically when you’re on this combination.
How Low Magnesium Shows Up
Normal serum magnesium falls between 1.46 and 2.68 mg/dL. Levels below 1.46 mg/dL qualify as low, but most people don’t feel anything until magnesium drops below about 1.2 mg/dL. Early signs include nausea, loss of appetite, fatigue, and general weakness. As levels fall further, you may notice muscle tremors, twitching, or cramping from increased nerve excitability, which is often the first obvious clinical sign. Severe depletion can affect heart rhythm.
These symptoms overlap with many other conditions, which makes magnesium depletion easy to miss without a blood test. If you’re on any blood pressure medication that includes a diuretic and you’re experiencing persistent fatigue, muscle cramps, or weakness, a simple blood draw can check your levels.
What This Means for You
If you take losartan by itself, magnesium depletion is not a concern supported by clinical evidence. You don’t need to start a magnesium supplement purely because of losartan. If you take losartan combined with hydrochlorothiazide, periodic electrolyte monitoring is standard practice, and your magnesium, potassium, and sodium levels should be checked as part of routine follow-up.
One thing worth noting: losartan does appear to increase zinc loss significantly enough to cause deficiency. If you’re looking into mineral depletion from losartan, zinc is the nutrient with stronger evidence behind it, not magnesium.