Your body depends on electrolytes such as potassium for water balance, as well as proper cell, nerve and muscle function. Blood levels must therefore remain in a tight range. Usually, your body can tap into potassium reserves inside your cells to cover small deficiencies without symptoms, says the Merck Manual. However, low blood potassium, or hypokalemia, can disrupt brain, heart and kidney function.
Values
Reference ranges for blood potassium can vary from lab to lab. However, according to David Goldmann, First Consult's editor in chief and a physician, a blood potassium concentration below 3.5 mEq/L (milliequivalents per liter) is considered low for an adult. Ranges for adults normally vary from 3.5 to 5.0 mEq/L. In contrast, children's values normally range from 3.9 to 5.9 mEq/L in newborns, 4.1 to 5.3 mEq/L in infants and 3.4 to 4.7 mEq/L in children.
Neuromuscular Effects
Because of potassium's key role in nerve and muscle function, a deficiency in potassium can reduce your skeletal muscles' ability to contract. As a result, you're likely to experience muscle weakness, especially when exercising. You may also experience cramping and twitches. A more severe but possible symptom is paralysis of the arms and legs, and occasionally trunk and respiratory muscles. Breathing difficulties can also occur, leading to respiratory failure if care is not taken. Other common symptoms include constipation, abdominal pain and bloating.
Kidney Effects
Because the kidneys are responsible for water and electrolyte balance, a deficiency in potassium usually has renal effects. When potassium is low, your kidneys filter more fluid out of the body, leading to frequent urination and nocturia, which is the medical term for excessive urination at night. Low potassium can also lead to excessive thirst, dehydration and a drop in blood pressure.
Cardiac Effects
As a muscle, your heart also depends on electrolytes such as potassium to function normally. Low potassium levels in your blood can lead to a number of cardiac problems, including heart rate disturbances, palpitations and cardiac arrest.
Causes
Common causes of low potassium include alcohol abuse, poor diet, severe diarrhea, vomiting, kidney malfunction, magnesium deficiency, aldosterone deficiency, laxative abuse and certain medications. For instance, diuretic treatments for high blood pressure and congestive heart failure commonly cause potassium loss. According to Maxine Papadakis, University of California professor of clinical medicine, trauma and excessive insulin can also lead to low blood potassium.
Treatment
Naturally, if an underlying disease is at the root of your potassium loss, it must be treated. However, in most cases of mild to moderate hypokalemia, the treatment consists of oral potassium pills. Papadakis notes that it can take several days or weeks of oral potassium supplements to fully replenish potassium reserves. Potassium injections may become necessary for severe hypokalemia or if you can't take potassium by mouth.
Considerations
Many fruits and vegetables, such as bananas, potatoes and tomatoes, can provide your body with potassium. However, according to Papadakis, dietary potassium is typically coupled to phosphate, instead of chloride. As a result, eating potassium-rich foods is not likely to resolve low potassium linked to chloride depletion, such as from vomiting or "water pills."
References
- "Quick Answers to Medical Diagnosis and Therapy"; Dr. Maxine Papadakis et al; 2010
- First Consult: Hypokalemia
- University of Michigan Health System: Potassium
- Merck Manual of Medical Information: Potassium
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