Several widely prescribed medication classes can cause low potassium, with diuretics (water pills) being the most common culprit. Normal blood potassium ranges from 3.5 to 5.2 mEq/L, and levels between 3 and 3.5 mEq/L are considered mild hypokalemia, while anything below 3 mEq/L is severe. About 40% of people taking diuretics develop low potassium at some point during treatment, making it one of the most frequent medication side effects.
Drugs lower potassium through three main pathways: forcing your kidneys to flush it out in urine, pushing it from your bloodstream into your cells (where blood tests can’t detect it), or increasing how much you lose through your gut. Understanding which medications carry this risk helps you know what to watch for.
Diuretics (Water Pills)
Diuretics are the single biggest medication-related cause of low potassium. Both loop diuretics (like furosemide) and thiazide diuretics (like hydrochlorothiazide) work by making your kidneys excrete more fluid, but they pull potassium out along with it. These drugs are commonly prescribed for high blood pressure, heart failure, and swelling, so millions of people take them daily.
Not all diuretics lower potassium. Potassium-sparing diuretics, including amiloride, triamterene, spironolactone, and eplerenone, actually conserve potassium. Doctors often pair one of these with a thiazide or loop diuretic specifically to prevent potassium from dropping too low. Interestingly, research suggests that potassium-sparing diuretics protect against dangerous heart rhythms more effectively than simply adding potassium supplements to a thiazide, possibly because they also prevent magnesium loss.
Acetazolamide, a less common diuretic used for glaucoma and altitude sickness, can also cause low potassium through a different kidney mechanism.
Corticosteroids and Hormonal Medications
Corticosteroids, including prednisone and similar anti-inflammatory drugs, cause your kidneys to retain sodium and dump potassium. The longer you take them and the higher the dose, the more significant the potassium loss tends to be. This is the same mechanism your body uses naturally: the adrenal hormone aldosterone regulates potassium excretion, and corticosteroid medications mimic or amplify that effect.
Fludrocortisone, a medication that specifically mimics aldosterone, carries an even stronger risk because its primary purpose is to make the kidneys hold onto sodium at potassium’s expense.
Inhaler Medications and Asthma Drugs
Beta-2 agonists, the bronchodilators found in rescue inhalers and nebulizer treatments for asthma and COPD, temporarily shift potassium from your bloodstream into your cells. At standard inhaler doses, the effect is usually small. But nebulized treatments deliver much higher doses, and repeated use during an asthma flare can push potassium levels down meaningfully.
Caffeine and related compounds called xanthines (theophylline is one still occasionally used for breathing problems) cause the same type of cellular potassium shift. For most people, normal caffeine intake isn’t a concern, but theophylline at prescription doses can be.
Certain Antibiotics and Antifungals
Some anti-infective medications damage the kidney’s ability to hold onto potassium. Amphotericin B, a powerful antifungal given intravenously for serious infections, is one of the most notorious. It creates tiny pores in kidney cell membranes, essentially poking holes that let potassium leak out into urine. Studies report that 12% to 40% of patients receiving amphotericin B develop potassium levels below 3 mEq/L, often requiring aggressive supplementation throughout treatment.
Other antimicrobials linked to potassium loss include certain aminoglycoside antibiotics and some antifungal agents, all through kidney-related mechanisms. If you’re hospitalized and receiving IV antibiotics, your care team will typically monitor your potassium with regular blood draws.
Laxatives
Laxatives cause potassium loss the simplest way possible: through the stool. Occasional use rarely causes problems, but regular or heavy laxative use can steadily deplete your potassium stores. This is especially relevant for people who use stimulant laxatives frequently for chronic constipation, or in cases of laxative misuse. Because the loss is gradual, potassium can drop significantly before symptoms become obvious.
Insulin at High Doses
Insulin activates a pump on cell surfaces that pulls potassium from the bloodstream into cells. At the doses people normally use for diabetes management, this effect is modest and temporary. However, at high doses or in overdose situations, the shift can be dramatic enough to cause dangerously low potassium. In fact, doctors intentionally use this mechanism in emergency rooms, giving insulin along with glucose to treat dangerously high potassium levels.
Licorice Root
This one isn’t a prescription drug, but it catches people off guard. Real licorice root (found in some herbal teas, supplements, and imported candies) contains a compound that blocks an enzyme in your kidneys, causing them to excrete extra potassium. The effect mimics what happens with corticosteroid medications. It takes consistent consumption to become a problem, but people who regularly drink licorice tea or chew natural licorice can develop genuinely low potassium along with high blood pressure. Most licorice-flavored candy in the U.S. uses artificial flavoring and doesn’t carry this risk.
Who Is Most at Risk
Certain health conditions amplify your risk of medication-induced low potassium. People with heart failure, diabetes, chronic kidney disease, liver disease, and COPD are especially vulnerable, partly because they often take multiple medications that affect potassium and partly because their underlying conditions alter how the body handles electrolytes.
Low magnesium is a particularly important risk multiplier. When magnesium is low, your kidneys have difficulty holding onto potassium regardless of what’s causing the loss. Research shows that hypokalemia and low magnesium occur together frequently, and correcting potassium without also addressing magnesium often fails. If your potassium keeps dropping despite supplementation, low magnesium is one of the first things to check.
Taking more than one potassium-lowering medication at the same time compounds the risk. Someone on a thiazide diuretic for blood pressure and a corticosteroid for an autoimmune condition, for example, is losing potassium through two separate kidney pathways simultaneously.
Signs of Low Potassium
Mild drops in potassium often produce no symptoms at all, which is part of why routine blood work matters when you’re on high-risk medications. As levels fall further, the most common signs include muscle weakness, cramps, fatigue, and constipation. Potassium plays a central role in muscle contraction, so your muscles are usually the first to complain.
Severe hypokalemia (below 3 mEq/L) can cause dangerous heart rhythm disturbances, significant muscle weakness, and in extreme cases, paralysis. People with existing heart conditions are at higher risk for cardiac complications even at moderately low levels, which is why potassium monitoring is standard practice for heart failure patients on diuretics. About 17% of patients with cardiovascular conditions develop hypokalemia during their care.
How Potassium Loss Is Managed
The approach depends on the cause and severity. For people on diuretics, doctors may switch to or add a potassium-sparing diuretic rather than simply prescribing potassium supplements. This strategy addresses the root cause and, as a bonus, helps preserve magnesium levels too.
When the culprit is a medication you need to continue taking, like a corticosteroid for an inflammatory condition or amphotericin B for a serious infection, potassium supplementation and increased dietary intake of potassium-rich foods (bananas, potatoes, beans, leafy greens) become the main tools. Your doctor will use periodic blood tests to track your levels and adjust the plan.
For medications that shift potassium into cells rather than flush it out entirely (like inhalers or insulin), the effect is usually temporary. Your total body potassium hasn’t actually decreased; it’s just temporarily hiding inside cells. Levels typically normalize once the medication wears off, though repeated high doses can create a sustained dip that needs attention.