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In medicine, hypokalemia is defined as a potassium level below .5 mmol/L in the blood. It's a simple number, but its significance can be great. As StatPearls describes: "Hypokalemia is defined as a serum potassium level less than 3.5 mEq/L." Many people experience no symptoms at all with a mild decrease, but when potassium falls faster or drops lower, the risk of affecting the heart and muscles increases.
What is a normal potassium level?
For adults, the reference range is usually between 3.5 and 4.4 mmol/L. This means that values within this range are considered normal and stable for the body's functions. In newborns and infants, the levels are slightly higher because their physiology and kidney function differ; children under seven days old can have values up to 5.9 mmol/L without it indicating illness.
Potassium is also sensitive to external influences. The test can be affected by blood stagnation, heavy muscle activity during sampling or hemolysis (when blood cells break down), which sometimes leads to falsely high potassium values. With very high amounts of platelets or white blood cells, you can even get so-called pseudohyperkalemia – where the value looks high in the test tube but is not in the body.
How to interpret deviating values?
When potassium is too high
Although this article is mainly about hypokalemia, it is important to know that elevated potassium values (hyperkalemia) can occur in conditions such as kidney failure, acidosis, adrenal insufficiency, circulatory shock and increased tissue breakdown, for example after major injuries or severe hemolysis. In these patients, potassium can rise rapidly, sometimes to dangerous levels that affect the heart.
When potassium is too low
Low levels occur primarily when the body loses more potassium than it takes in, or when hormonal and acid-base balances cause the kidneys to excrete more than necessary. Prolonged diarrhea, vomiting, and laxatives are classic causes. Long-term parenteral nutrition without proper electrolyte replacement can also lead to deficiency.
Hormonal conditions such as Cushing's syndrome, hyperaldosteronism, and certain inherited salt balance disorders such as Bartter's syndrome cause the body to actively release potassium through the kidneys. Diuretic therapy without potassium replacement is one of the most common drug causes. Metabolic alkalosis – when the blood becomes too alkaline – also drives potassium into the cells and causes the blood value to drop.
Why does potassium drop?
There are several reasons why potassium drops. The medical mechanisms are usually divided into three categories: loss of potassium from the body, displacement of potassium into the cells and insufficient intake. Diarrhea, vomiting and diuretics are the most common causes of actual loss. Other times it is a matter of displacement – for example, with insulin treatment, beta-agonists or metabolic alkalosis. Malnutrition and prolonged alcohol consumption can also contribute, although they rarely alone cause hypokalemia.
How is hypokalemia diagnosed?
Symptoms vary depending on the level and how quickly it has dropped. Some people barely notice anything at all, while others experience clear symptoms such as muscle weakness, cramps, constipation and palpitations. In more severe cases, the heart rhythm can be affected, which is why healthcare providers take hypokalemia very seriously – especially in people with cardiovascular disease or those taking digoxin.
How is low potassium diagnosed
In addition to measuring potassium via a blood test, magnesium, kidney function and the body's acid-base balance are often examined. Urine tests can show whether the loss is occurring via the kidneys or via the gastrointestinal tract. EKG is used when the doctor needs to assess how the heart is reacting, and hypokalemia can give a characteristic pattern with flatter T waves and the appearance of U waves
Treatment - how to restore potassium balance
The treatment depends entirely on the cause and how low the value is. First and foremost, the triggering factor is addressed: medications can be adjusted, fluid deficiency is treated and hormonal disorders are investigated. An important part of the treatment is to control magnesium, which often drops at the same time. Low magnesium makes it more difficult for the body to retain potassium, which means that potassium supplements are sometimes not enough until the magnesium has been corrected.
Potassium is usually administered in tablet or liquid form. Intravenous treatment is used in severe hypokalemia or if the patient has heart problems. The goal is to safely normalize the value – often to levels above 4.0 mmol/L in people with heart disease to reduce the risk of arrhythmias.
What can be done to avoid potassium deficiency?
For many, it is about restoring balance in case of temporary disturbances. Potassium-rich foods such as bananas, avocados, potatoes, legumes and green leafy vegetables are a good complement. In the case of long-term stomach illness, fluid replacement is preferable to plain water, since the salt and mineral balance is at least as important as the fluid itself. Being careful with large amounts of licorice, keeping track of medications and making sure to consume magnesium-rich foods can also prevent imbalance. People who exercise a lot or use diuretics should be extra careful.