Am Fam Physician. 2023;107(1):59-70
Patient information: See related handout on what happens when a person has too much or not enough potassium.
Author disclosure: No relevant financial relationships.
Hypokalemia and hyperkalemia occur when serum potassium levels are less than 3.5 mEq per L or greater than 5.0 mEq per L, respectively. The World Health Organization recommends a potassium intake of at least 3,510 mg per day for optimal cardiovascular health. Hypokalemia is caused by decreased intake, renal losses, gastrointestinal losses, or transcellular shifts. Severe features of hypokalemia that require urgent treatment include a serum potassium level of 2.5 mEq per L or less, electrocardiography abnormalities, or neuromuscular symptoms. The underlying cause should be addressed, and potassium levels replenished. An oral route is preferred if the patient has a functioning gastrointestinal tract and a serum potassium level greater than 2.5 mEq per L. Hyperkalemia is caused by impaired renal excretion, transcellular shifts, or increased potassium intake. Electrocardiography identifies cardiac conduction disturbances but may not correlate with serum potassium levels. Emergent treatment is recommended for patients with clinical signs and symptoms (e.g., muscle weakness, paralysis) or if electrocardiography abnormalities are present. Acute treatment may include intravenous calcium, insulin, sodium bicarbonate, diuretics, and beta agonists. Dialysis may be considered in the presence of end-stage renal disease, severe renal impairment, or ongoing potassium release. Patiromer and sodium zirconium cyclosilicate are newer potassium binders and may be used in chronic or acute hyperkalemia. Sodium polystyrene sulfonate is associated with serious gastrointestinal adverse effects. Long-term management of potassium disturbances includes correcting underlying conditions, dietary counseling, and adjusting causative medications.
Homeostasis maintains a normal range of serum potassium defined as 3.5 to 5.0 mEq per L.1–3 The prevalence of hyperkalemia in the general population is 3.3%, and hypokalemia is 1.9%; however, in the emergency department, the prevalence is 3.6% and 5.5%, respectively.4,5 In patients with chronic kidney disease (CKD), the prevalence of hyperkalemia is 18%.5 The inpatient prevalence of hyperkalemia and hypokalemia ranges from 6.9% to 12.3% and 2.9% to 7.4%, respectively.6,7 Patients with an abnormal potassium level on admission (adjusted odds ratio [OR] = 1.49; 95% CI, 1.26 to 1.75) and patients with hyperkalemia (adjusted OR = 1.44; 95% CI, 1.11 to 1.87) requiring admission to a cardiac intensive care unit have an elevated risk of mortality.6,8 Serum potassium levels have a U-shaped curve association with morbidity and mortality.5,6 The best outcomes in observational studies are associated with a serum potassium level between 4 and 5 mEq per L, specifically for patients with heart failure or CKD.5,9–11 In the general population, moderate hyperkalemia (greater than 5.5 mEq per L; adjusted hazard ratio [HR] = 1.22; 95% CI, 1.15 to 1.29) and hypokalemia (less than 3.0 mEq per L; adjusted HR = 1.49; 95% CI, 1.26 to 1.76) are associated with an increased risk of all-cause mortality.5
| Patiromer (Veltassa) and sodium zirconium cyclosilicate (Lokelma) are preferred over sodium polystyrene sulfonate for the treatment of chronic hyperkalemia due to higher efficacy and lower risk of serious adverse effects. |
Dietary Recommendations
The World Health Organization recommends a potassium intake of at least 3,510 mg per day for adults for optimal cardiovascular health.12–14 High dietary potassium intake has been found to lower blood pressure in patients with hypertension, although it may precipitate hyperkalemia if renal function is impaired.3,13–15 An increased dietary potassium intake is associated with a lower risk of stroke.12 Potassium-rich foods are common to a healthy diet (Table 1).12,16,17 A low-potassium diet is generally recommended for patients with advanced CKD (Table 2).12,16,17 More research is needed for dietary potassium restriction in CKD.18
| Food group | Food item | Food group | Food item |
|---|---|---|---|
| Seasonings/condiments Desserts Nuts, seeds, and legumes Grains | Low-sodium salt (contains potassium chloride) Sea salt Molasses Chocolate Lima beans Sunflower seeds Pistachios Pumpkin seeds Wheat germ Bran Oats | Vegetables Meats Fruit | Seaweed Spinach Tomatoes Broccoli Potatoes Beef Chicken Pork Lamb Bananas Cantaloupes Oranges Avocados Dried fruits (dates, prunes) |
| Stage | Dietary potassium recommendations | Comments |
|---|---|---|
| 1 eGFR ≥ 90 mL per minute per 1.73 m2 Albuminuria < 30 mg per g | Same as general population; 3,510 mg per day | Safe for potassium-rich foods (e.g., avocado, banana, spinach, leafy greens, potatoes, citrus juices, fish) |
| 2 eGFR 60 to 89 mL per minute per 1.73 m2 Albuminuria < 30 mg per g | Same as general population; 3,510 mg per day | Safe for potassium-rich foods (e.g., avocado, banana, spinach, leafy greens, potatoes, citrus juices, fish) |
| 3a eGFR 45 to 59 mL per minute per 1.73 m2 Albuminuria < 30 mg per g 3b eGFR 30 to 44 mL per minute per 1.73 m2 Albuminuria < 30 mg per g | Same as general population unless episodes of severe hyperkalemia occur | Recommend fresh fruits and vegetables; limit milk and dairy products; avoid salt substitutes due to potassium chloride content; encourage a high-fiber diet* |
| 4 eGFR 15 to 29 mL per minute per 1.73 m2 Any stage with A2 (albuminuria 30 to 300 mg per day) or A3 (albuminuria > 300 mg per day) | < 3,000 mg per day if hyperkalemia occurs frequently | Recommend low-potassium foods (e.g., apples, berries, carrots, green beans, chicken, eggs, white grain breads, white rice); limit serving sizes; avoid salt substitutes and sea salt |
| 5 eGFR < 15 mL per minute per 1.73 m2 | < 3,000 mg per day | Recommend low-potassium foods (e.g., apples, berries, carrots, green beans, chicken, eggs, white grain breads, white rice); limit serving sizes; avoid salt substitutes and sea salt |
Hypokalemia
CAUSES
Hypokalemia is caused by decreased intake, renal losses, gastrointestinal losses, or transcellular shifts (Table 3).19–21 Diuretics are among the most common causes of hypokalemia, especially at higher doses.18,22 Thiazide diuretics are associated with an 11-fold increased risk of hypokalemia and a fivefold increased risk of moderate hypokalemia (less than 3.0 mEq per L).23 Gastrointestinal losses are most often caused by acute or chronic diarrhea. Hypokalemia can occur with low-volume colonoscopy preparation in patients taking diuretics or patients who are hospitalized.24 Female sex and oral laxative use have been associated with preoperative hypokalemia in older patients.25
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