Hypokalemia is a low level of potassium (K+) in the blood serum. Mild low potassium does not typically cause symptoms. Symptoms may include feeling tired, leg cramps, weakness, and constipation. Low potassium also increases the risk of an abnormal heart rhythm, which is often too slow and can cause cardiac arrest.Causes of hypokalemia include vomiting, diarrhea, medications like furosemide and steroids, dialysis, diabetes insipidus, hyperaldosteronism, hypomagnesemia, and not enough intake in the diet. Normal potassium levels are between 3.5 and 5.0 mmol/L (3.5 and 5.0 mEq/L) with levels below 3.5 mmol/L defined as hypokalemia. It is classified as severe when levels are less than 2.5 mmol/L. Low levels may also be suspected based on an electrocardiogram (ECG). Hyperkalemia is a high level of potassium in the blood serum.The speed at which potassium should be replaced depends on whether or not there are symptoms or abnormalities on an electrocardiogram. Potassium levels that are only slightly below the normal range can be managed with changes in the diet. Lower levels of potassium require replacement with supplements either taken by mouth or given intravenously. If given intravenously, potassium is generally replaced at rates of less than 20 mmol/hour. Solutions containing high concentrations of potassium (>40 mmol/L) should generally be given using a central venous catheter. Magnesium replacement may also be required.Hypokalemia is one of the most common water–electrolyte imbalances. It affects about 20% of people admitted to hospital. The word hypokalemia comes from hypo- under +  kalium potassium + -emia blood condition.
Giving IV potassium at faster rates (20–25 meq/hr) may inadvertently expose the heart to a sudden increase in potassium, potentially causing dangerous abnormal heart rhythms such as heart block or asystole. Faster infusion rates are therefore generally only performed in locations in which the heart rhythm can be continuously monitored such as a critical care unit. When replacing potassium intravenously, particularly when higher concentrations of potassium are used, infusion by a central line is encouraged to avoid the occurrence of a burning sensation at the site of infusion, or the rare occurrence of damage to the vein. When peripheral infusions are necessary, the burning can be reduced by diluting the potassium in larger amounts of fluid, or adding a small dose of lidocaine to the intravenous fluid, although adding lidocaine may increase the likelihood of medical errors. Even in severe hypokalemia, oral supplementation is preferred given its safety profile. Sustained-release formulations should be avoided in acute settings. Potassium-sparing diuretics
Hypokalemia which is recurrent or resistant to treatment may be amenable to a potassium-sparing diuretic, such as amiloride, triamterene, spironolactone, or eplerenone. Concomitant hypomagnesemia will inhibit potassium replacement, as magnesium is a cofactor for potassium uptake. Popular culture
The plot of the science fiction novel Destinys Road by Larry Niven centers around the settings scarcity of available potassium, and the resulting deficiency and its effects on the worlds colonists and their society.In the video game Deltarune, Queen expresses concern about one of the characters (Noelle) clipping into a wall and dying slowly from Hypokalemia.