Symptoms of potassium deficiency and high potassium

Potassium – the body’s “electricity supply” for nerves, muscles and heart

Potassium is one of the body’s most important electrolytes – a mineral that helps cells communicate and muscles work. Many people think of potassium only when they experience calf cramps, weakness or palpitations, but the truth is that both low potassium (hypokalemia) and high potassium (hyperkalemia) can sometimes develop without any obvious symptoms. Because potassium affects the heart’s electrical system and the body’s fluid balance, it is a biomarker that is often analyzed when electrolyte imbalances, kidney damage or drug effects are suspected.

What is potassium and why is it so important?

Potassium is mainly found inside the body’s cells and only a small amount circulates in the blood. Nevertheless, a venous blood test provides important information about the balance in the body. Potassium is needed for, among other things:

• Normal nerve signaling (impulses between nerve and muscle)
• Muscle work, including bowel movements and the heartbeat
• Regulation of fluid balance together with sodium
• Stable heart rhythm (electrical activity in the heart)

Normal potassium value - what does the reference range mean?

Potassium is measured in the blood in the unit mmol/L. The exact reference range may vary slightly between laboratories, but is often around 3.5–5.0 mmol/L. If the value is below the reference, it is called hypokalemia and if it is above the reference, it is called hyperkalemia.

It is important to interpret potassium together with symptoms, other blood tests (e.g. creatinine/eGFR for kidney function) and medications. Sometimes potassium can also be “falsely” elevated due to sample handling, for example if blood cells break down in the sample (so-called pseudohyperkalemia). In that case, a repeat test may be needed.

Can low potassium lead to potassium deficiency (hypokalemia)?

Low potassium is most often linked to the body losing potassium (via the intestines, urine or sweat) or to potassium being displaced into the cells. In healthy people, pronounced potassium deficiency is not the most common, but it can occur with fluid loss or with certain medications.

Common symptoms of potassium deficiency

The symptoms can be diffuse and misinterpreted as “stress”, “too little sleep” or “overtraining”. In more severe cases, you may experience:

• Fatigue and lack of energy
• Muscle cramps (e.g. in the calves), muscle twitching
• Muscle weakness or “heavy legs”
• Constipation (the muscles of the intestine are affected)
• Heart palpitations or irregular pulse (especially in more severe cases)

These are the most common causes of low potassium (potassium deficiency)

Low potassium, also called potassium deficiency or hypokalemia, most often occurs when the body loses more potassium than it takes in, or when the balance is disrupted by illness or medication. Below are the most common causes of low potassium levels.

• Prolonged diarrhea or vomiting, where the body loses large amounts of fluid and electrolytes, including potassium.
• Diuretics, which are often used for conditions such as high blood pressure or heart failure, can increase the excretion of potassium in the urine.
• Fluid deficiency combined with strenuous physical exertion, where heavy sweating without sufficient replacement of fluid and salts can lead to electrolyte imbalance.
• Insufficient potassium intake, malnutrition or eating disorders, where the body does not get enough potassium through the diet for a long time.
• Hormonal disorders that affect the body's salt and fluid balance, which can cause more potassium than normal to be lost through the kidneys.

Since the symptoms of potassium deficiency are often non-specific, such as fatigue, muscle weakness or cramps, a venous blood test can be an important step in identifying the cause and determining whether further investigation or follow-up is needed.

If potassium is too high, there is a risk of (hyperkalemia)

High potassium is usually due to the kidneys not having time to get rid of potassium at the rate needed, or potassium leaking from cells. In completely healthy people, high potassium is more unusual, but it is an important marker to detect because high levels can affect the heart's rhythm.

Common Symptoms of High Potassium

Many people have no symptoms with mild elevations. As levels rise, you may experience:

• Muscle weakness or a “flabby feeling”
• Tingling or numbness
• Nausea
• Irregular heartbeat, palpitations, or slow pulse

In severe cases of high potassium, the heart’s electrical system can be seriously affected. If you experience new, severe palpitations, fainting, or chest pain, seek emergency medical attention.

Common causes of high potassium

• Impaired kidney function (acute or chronic)
• Diabetes with kidney effects
• Certain blood pressure/heart medications that affect potassium excretion
• Potassium-sparing diuretics or combinations of medications
• Test interference (pseudohyperkalemia) that requires retesting

Are abnormal potassium levels common?

In healthy people with normal kidney function, clearly low or high potassium levels are not the most common. However, potassium disorders are relatively common in people with kidney disease, heart disease, diabetes or in those who are on medications that affect fluid and salt balance. Since the symptoms are often non-specific (fatigue, cramps, weakness), a blood test can be crucial to understanding what is actually going on.

Potassium and diet – is it enough to “eat more bananas”?

Potassium is found in many foods (e.g. fruit, vegetables, legumes, potatoes, fish and dairy products). For most people, a varied diet is enough to cover the need. However, if the disorder is due to diarrhoea/vomiting, kidney damage or medication, it is rarely a good idea to self-medicate with dietary supplements. Especially if high potassium is suspected, extra intake may be inappropriate – so it is wise to first find out your levels.

Potassium test - how it works

Potassium is measured with a venous blood test (prick in the arm). The test is often used to assess electrolyte balance, kidney function and drug effects, and can be particularly relevant for symptoms such as cramps, muscle weakness, palpitations or long-term gastrointestinal problems.

At Testmottagningen, you can order a potassium test via venous sampling as a private referral. It is an easy way to get clear information about your electrolyte balance. If the value deviates, it may sometimes need to be checked again (e.g. if the test has been affected), and then we will help you understand the next step.

What does potassium say about how you are feeling?

Potassium reflects an important part of the body's "internal balance". Changed values ​​can provide clues about fluid deficiency, gastrointestinal losses, drug effects or kidney effects - and in some cases affect the heart's rhythm. For a correct assessment, potassium needs to be interpreted in context, preferably together with symptoms and other tests. Potassium can be ordered as a venous blood test atTestmottagningen