High potassium: what it means and what to do

A high potassium result is often false: during the draw, potassium can leak out of cells into the tube. That is why a first high result is usually repeated. If it is real, kidneys that filter less or blood pressure medicines are often behind it. Above 5.5 it needs a doctor today.

What high potassium means

Potassium sits almost entirely inside your cells. If too much leaks out, or your kidneys cannot clear it, the level in your blood rises.

The first step is to check whether it is real: a repeat test is often normal. If it stays high, your doctor looks for the cause, usually the kidneys or medicines.

What causes high potassium

The first is the most common, and it does not mean a disease.

Symptoms

Often none, even when it is high. That is why it is almost always found on a blood test.

When it is very high there can be muscle weakness, tingling, nausea, palpitations or an irregular heartbeat.

With a high potassium, palpitations, very weak muscles or fainting are an emergency: call 112 or go to the emergency department.

False high potassium: when the draw is to blame

This happens often. If you clench your fist or the vein is hard to find, potassium leaks out of cells. The same happens if the tube is shaken, stored badly or analysed many hours later. The number rises in the tube, not in your body.

Sometimes the report flags it, with a note such as haemolysed sample. Very high platelets or white cells can also raise potassium in the tube.

A new draw, with your hand relaxed, usually settles it. But you cannot assume it is false: above 5.5 see a doctor today, and above 6 go to the emergency department.

Which tests to read alongside it

These tests help show whether the number is real and where it comes from.

What your result means

The upper end of the scale, in mmol/L.

What to do if your potassium is high

First find out whether it is real, then remove the cause, with your doctor. Where to start:

When to worry

Talk to a doctor if:

With Rosa, a potassium above 5.5 mmol/L is always flagged to a doctor, urgently.

Frequently asked questions

High potassium: when should I worry? Just above the limit, talk to your doctor: the repeat test is often normal. Above 5.5 see a doctor today, even if you feel fine, and above 6 go to the emergency department. With palpitations, very weak muscles or fainting, call 112 or go to the emergency department.

Slightly high potassium: can it be an error? Yes, it happens often: potassium can leak out of cells during the draw. That is why your doctor usually repeats it, and looks for a cause if it stays high.

What are the symptoms of high potassium? Often none. When it is very high there can be weakness, tingling, nausea or palpitations. With palpitations, very weak muscles or fainting, call 112 or go to the emergency department.

High potassium: what should I avoid eating? If your kidneys are fine, you usually do not need to change your diet: the cause matters. If they filter less, your doctor may ask you to limit some potassium-rich foods, such as nuts, legumes and potatoes, and salt substitutes.

Is high potassium dangerous? If it is real and very high, yes: it can make your heartbeat irregular. That is why above 5.5 it should be seen today, and above 6 at the emergency department, even though the repeat test is often normal.

I take blood pressure medicines: is that why my potassium is high? It may be: some, such as ACE inhibitors, sartans and spironolactone, hold on to potassium. That is why your doctor checks it. Do not stop them on your own: bring your doctor the report.

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