Severe hypokalemia (<3. 0 mEq/l) may require intravenous supplementation. Typically, a saline solution is used, with 20–40 meq/l KCl per liter over 3–4 hours. 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.
Hypokalemia is a low level of potassium (K + ) in the blood serum .  Mildly low levels do not typically cause symptoms.  Symptoms may include feeling tired , leg cramps , weakness, and constipation .  It increases the risk of an abnormal heart rhythm , which is often too slow , and can cause cardiac arrest .  
Hypokalemia is when blood’s potassium levels are too low. Potassium is an important electrolyte for nerve and muscle cell functioning, especially for muscle cells in the heart. Your kidneys control your body’s potassium levels, allowing for excess potassium to leave the body through urine or sweat.