Several widely used medications can lower your magnesium levels, sometimes significantly. The most common culprits are acid reflux drugs (proton pump inhibitors), certain diuretics, some antibiotics, anti-rejection drugs used after organ transplants, and specific chemotherapy agents. Normal blood magnesium falls between 1.7 and 2.2 mg/dL, and symptoms of deficiency typically don’t appear until levels drop below 1.2 mg/dL, which means the problem can build silently over months.
Proton Pump Inhibitors (PPIs)
PPIs are among the most prescribed medications worldwide, used to treat acid reflux, GERD, and stomach ulcers. Brand names you’d recognize include omeprazole (Prilosec), esomeprazole (Nexium), lansoprazole (Prevacid), and pantoprazole (Protonix). In 2011, the FDA issued a formal safety warning that long-term PPI use, typically longer than one year, can cause low magnesium.
The mechanism is straightforward: PPIs reduce acid in the stomach and upper intestine, which raises the pH in those areas. Magnesium needs an acidic environment to dissolve properly so your gut can absorb it. When the environment becomes less acidic, magnesium passes through without being absorbed. This is different from most other drugs on this list, which cause your kidneys to waste magnesium. PPIs block it from getting into your body in the first place.
The risk is highest if you take a PPI alongside another magnesium-depleting medication like a diuretic, or if you have diabetes, kidney problems, or low dietary magnesium intake. If you’ve been on a PPI for more than a year, periodic blood testing for magnesium is reasonable, especially if you have any of those additional risk factors.
Diuretics (Water Pills)
Diuretics are a complicated category because different types affect magnesium differently. Loop diuretics, such as furosemide (Lasix) and bumetanide, have the strongest potential to deplete magnesium. They work in a part of the kidney where a significant amount of magnesium gets reabsorbed, and by increasing urine output from that segment, they can flush magnesium out with it. The risk is highest with large doses taken multiple times a day over long periods, which is common in people with heart failure.
Thiazide diuretics, like hydrochlorothiazide, are prescribed far more often (mainly for high blood pressure) and get a lot of blame for magnesium loss. The evidence is actually less clear-cut. At standard doses, most people on thiazides do not develop magnesium deficiency and don’t need supplements. The risk increases at higher doses (25 mg/day or more of hydrochlorothiazide), in people over 60, and in those with other contributing factors like poor dietary intake or insulin resistance.
Potassium-sparing diuretics, such as spironolactone and amiloride, actually tend to preserve or even raise magnesium levels. If you’re on a combination that includes one of these, it may partially offset the magnesium-wasting effect of a loop or thiazide diuretic.
Antibiotics and Antifungal Drugs
Two classes of anti-infective medications are well-known magnesium wasters: aminoglycoside antibiotics and the antifungal amphotericin B. These are typically given intravenously in hospitals for serious infections, so they’re less likely to affect people taking pills at home.
Aminoglycosides (gentamicin, tobramycin, amikacin) damage the cells of the kidney’s proximal tubule, the section responsible for reabsorbing many electrolytes including magnesium. The drugs are filtered by the kidneys and taken up by tubular cells, where they disrupt normal cell membrane function. The longer the course and the higher the dose, the greater the risk.
Amphotericin B, used for severe fungal infections, causes magnesium and potassium wasting by increasing the permeability of kidney cell membranes. Essentially, it pokes holes in the cell walls, letting electrolytes leak out into the urine. Magnesium loss is one of the most predictable side effects of this drug, and patients receiving it in the hospital are routinely monitored and given supplemental magnesium.
Immunosuppressants After Transplant
Calcineurin inhibitors, specifically tacrolimus and cyclosporine, are cornerstone medications for preventing organ rejection after a transplant. Low magnesium is extremely common in the first weeks and months after kidney transplantation, and these drugs are the primary reason.
They work by shutting down a specific magnesium channel in the kidney’s distal tubule, the final stretch where the kidney fine-tunes how much magnesium to keep versus excrete. With that channel suppressed, magnesium flows out in the urine instead of being reclaimed. Magnesium levels typically hit their lowest point around the second month after transplant, and the problem persists in more than 20% of kidney transplant recipients years later. Tacrolimus appears to be the bigger offender of the two. Faster decline in transplanted kidney function has been linked to this persistent magnesium depletion, which is why transplant teams monitor it closely.
Chemotherapy Agents
Two types of cancer drugs are particularly hard on magnesium levels: platinum-based chemotherapy and EGFR inhibitors.
Cisplatin, a platinum-based drug used for bladder, lung, ovarian, and other cancers, directly damages kidney tubule cells, causing magnesium to spill into the urine. The damage can sometimes persist after treatment ends, making it one of the longer-lasting drug-related causes of low magnesium.
Cetuximab, an EGFR inhibitor used for metastatic colorectal and head/neck cancers, works differently. The cells lining the kidney tubule have high levels of EGFR (epidermal growth factor receptor), and cetuximab blocks it. That receptor normally activates the same magnesium channel (TRPM6) that calcineurin inhibitors suppress. Without that activation signal, the kidney can’t reabsorb magnesium efficiently. The good news is that magnesium levels typically return to normal after cetuximab treatment stops, suggesting the damage is functional rather than structural. Patients receiving cetuximab alongside platinum-based drugs face the highest risk and are generally screened for magnesium regularly during treatment.
How Low Magnesium Develops Over Time
Drug-induced magnesium depletion rarely happens overnight. With PPIs, it typically takes over a year. With diuretics, it depends on the dose and how many other risk factors you have. Chemotherapy and aminoglycosides can cause faster drops because they directly damage kidney tissue. The insidious part is that blood levels can decline gradually without any symptoms until they reach a critically low threshold, generally below 1.2 mg/dL.
When symptoms do appear, they tend to start with muscle cramps, twitching, and fatigue. As levels drop further, you might experience numbness or tingling, abnormal heart rhythms, or even seizures in severe cases. Low magnesium also drags other electrolytes down with it. It’s closely linked to low potassium and low calcium, and those deficiencies can be stubbornly resistant to correction until magnesium is replenished.
What to Do If You Take These Medications
If you’re on one or more of these drug classes, a simple blood test can establish your baseline magnesium level. For people starting long-term treatment with a PPI, diuretic, or calcineurin inhibitor, rechecking after a few months and then periodically (roughly every three months during supplementation) is a practical approach.
When supplementation is needed, organic forms of magnesium like magnesium citrate or gluconate are generally recommended for better absorption. Mineral water with high magnesium content (over 100 mg per liter) can also contribute meaningfully to your daily intake. If you’re taking a PPI, the absorption issue in your gut means oral supplements may be less effective, and your doctor may need to explore alternatives or adjust your acid reflux treatment.
One practical note: magnesium supplements can interfere with the absorption of certain antibiotics, particularly tetracyclines. If you’re taking both, separating them by at least two hours helps avoid this interaction. The same principle applies to several other medications that bind to minerals in the gut.