High potassium, known medically as hyperkalemia, happens when blood potassium rises above 5.5 mEq/L. The normal range sits between roughly 3.7 and 5.3 mEq/L. Because your body keeps about 98% of its potassium inside cells (where concentrations reach 120 to 130 mEq/L), even small disruptions in how potassium moves between cells and blood, or how it’s excreted, can push levels dangerously high. The causes fall into a few major categories: kidney problems, medications, hormonal imbalances, cellular damage, and shifts in blood chemistry.
Kidney Disease Is the Most Common Cause
Your kidneys are the primary exit route for potassium. Healthy kidneys are remarkably good at adapting. Even as kidney function declines, the remaining working tissue compensates by increasing how much potassium each nephron (the kidney’s filtering unit) secretes. This adaptation holds up surprisingly well. Potassium balance is generally maintained until the glomerular filtration rate, a measure of overall kidney function, drops below 15 to 20 mL/min. That corresponds to late-stage chronic kidney disease.
Once kidney function falls past that threshold, the body simply can’t excrete potassium fast enough to keep up with dietary intake. This is why people with advanced kidney disease are often advised to limit potassium to less than 3 grams per day, and those on hemodialysis to around 2.7 to 3.1 grams per day. For context, a single baked potato with skin contains close to 900 milligrams, and a cup of cooked spinach has about 800 milligrams. People with earlier-stage kidney disease generally don’t need potassium restrictions unless their blood levels are already running high.
Medications That Raise Potassium
A long list of common medications can raise potassium, and many people taking them have no idea this is a side effect. The drugs work through different mechanisms, but the result is the same: potassium builds up in the blood.
- Blood pressure drugs that block the renin-angiotensin system. ACE inhibitors (like lisinopril and enalapril) and angiotensin receptor blockers (like losartan and candesartan) reduce potassium excretion by lowering aldosterone, the hormone that tells your kidneys to flush potassium out. These are among the most widely prescribed medications in the world, and the risk goes up significantly when kidney function is also impaired.
- NSAIDs. Over-the-counter painkillers like ibuprofen and naproxen can raise potassium through the same aldosterone-lowering pathway. The risk is higher with regular use rather than the occasional dose.
- Potassium-sparing diuretics. Spironolactone, eplerenone, amiloride, and triamterene are designed to prevent potassium loss, but they can overshoot, especially when combined with other potassium-raising drugs.
- Beta-blockers. Medications like metoprolol and atenolol interfere with the cellular machinery that pulls potassium from the blood into cells.
- Potassium supplements. Potassium chloride tablets or liquid, sometimes prescribed alongside diuretics that waste potassium, can easily tip the balance if the dose isn’t carefully matched to what your body needs.
The combination of an ACE inhibitor, a potassium-sparing diuretic, and an NSAID is a particularly well-known recipe for hyperkalemia, especially in older adults with even mild kidney impairment.
Low Aldosterone and Adrenal Problems
Aldosterone is the hormone that tells your kidneys, sweat glands, and colon to hold onto sodium and release potassium. When aldosterone production drops, potassium accumulates because the body loses its main signal to excrete it. Addison’s disease (primary adrenal insufficiency) is the classic example. The adrenal glands are damaged and can’t produce enough aldosterone, leading to high potassium, low sodium, low blood pressure, and acidosis.
Diabetes can also impair this system. The kidneys produce an enzyme called renin that kicks off aldosterone production, and diabetic kidney damage often reduces renin output. This creates a state sometimes called hyporeninemic hypoaldosteronism, which is one of several reasons people with diabetes face a higher-than-average risk of hyperkalemia.
Insulin Deficiency and Diabetes
Insulin does more than control blood sugar. After a meal, the burst of insulin from your pancreas actively drives potassium from the bloodstream into cells by powering up a pump (the sodium-potassium pump) embedded in cell membranes. Insulin also helps cells take in glucose, which fuels that same pump. When insulin is absent or insufficient, as in uncontrolled type 1 diabetes or advanced type 2 diabetes, potassium stays in the blood instead of being tucked away inside cells.
This is why diabetic ketoacidosis, a dangerous complication of uncontrolled diabetes, often presents with high potassium even though the body’s total potassium stores may actually be depleted. The combination of insulin deficiency, acidosis, and dehydration creates a perfect storm for potassium to flood the bloodstream.
Acidosis Pushes Potassium Out of Cells
When your blood becomes too acidic, a condition called metabolic acidosis, potassium shifts out of cells and into the bloodstream. The mechanism is more complex than the simple “hydrogen in, potassium out” swap described in older textbooks. What actually happens involves several transport systems working in parallel. As blood pH drops, the normal flow of sodium into cells slows down. That means the sodium-potassium pump has less sodium to work with and runs more slowly, so it pulls less potassium back into cells. Potassium then leaks out through channels that are always open, with nothing to counteract the leak.
The rise in blood potassium from acidosis is temporary. It reverses once the underlying acid-base problem is corrected. But in the short term, the spike can be significant enough to cause dangerous heart rhythm changes.
Massive Cell Damage
Because the concentration of potassium inside cells is roughly 120 to 130 mEq/L, far higher than the 3.7 to 5.3 mEq/L in blood, anything that destroys large numbers of cells at once dumps potassium into the circulation faster than the kidneys can clear it.
Rhabdomyolysis, the breakdown of skeletal muscle from crush injuries, extreme exertion, or certain drugs, is one of the most dramatic causes. Severe burns produce a similar effect across damaged skin and tissue. Tumor lysis syndrome occurs when cancer treatment kills a large volume of tumor cells rapidly, releasing their potassium, phosphorus, and other contents into the blood. This is most common with blood cancers like leukemia and lymphoma that respond quickly to chemotherapy. Even a major blood transfusion can contribute, since stored red blood cells gradually leak potassium into the surrounding fluid over time.
A Rare Genetic Cause
Hyperkalemic periodic paralysis is an inherited condition caused by mutations in the SCN4A gene, which controls sodium channels in muscle cells. The mutated channels stay open too long, allowing excess sodium to flood in. This triggers potassium release from muscle cells into the blood. During episodes, people experience temporary muscle weakness or paralysis along with elevated blood potassium. The condition follows an autosomal dominant inheritance pattern, meaning a child needs only one copy of the altered gene from one parent to be affected. In 30 to 40 percent of cases, no genetic mutation is identified.
False Readings Worth Knowing About
Not every high potassium result reflects what’s actually happening in your body. Pseudohyperkalemia is a falsely elevated reading caused by problems with the blood sample itself. Clenching your fist repeatedly during a blood draw, a tight tourniquet left on too long, or rough handling of the sample can rupture red blood cells (hemolysis), spilling their intracellular potassium into the tube. The lab report shows high potassium, but your actual blood level is normal.
If your potassium comes back high and you feel fine with no other abnormalities, there’s a reasonable chance the result is a lab artifact. A repeat draw with careful technique usually clarifies whether the elevation is real. This is especially common in emergency department settings where blood draws happen quickly under less-than-ideal conditions.