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I had a blood test to check for arthritis...

I had a blood test to check for arthritis. It came back negative but my GP said that it showed I had a raised level of sodium. He has requested a further blood test to see if it has changed. What does this mean and what is the impact?

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The answer

Your body carefully balances the sodium levels in the blood. The range for normal sodium levels is 135-145 millimoles per litre (mmol/L). Some people naturally have slightly high sodium levels in the blood – usually around 146-148 mmol/L.

A low level of sodium in the blood (also known as hyponatremia) is relatively common. A high level of sodium in the blood (hypernatremia) is much less common.

If you are otherwise feeling well it’s quite possible it was a glitch in processing your sample, and the next reading may be normal. But higher levels of sodium in the blood that don’t come down do need further investigation.

Hyponatremia – the symptoms and causes

Low sodium levels in the blood causes hyponatremia. This usually happens if you drink too much water in a short time.

The most common symptoms are:

  • Nausea
  • Vomiting
  • Headaches.

In really serious instances, low sodium levels can cause the brain to swell leading to confusion, fits, comas and sometimes death, though this is rare.

Hypernatremia – the symptoms and causes

Hypernatremia is defined as a serum sodium level above 146 mmol/L.

Hypernatremia can be caused by:

  • Dehydration, from diarrhoea and vomiting or diuretics (usually water tablets given for high blood pressure)
  • Kidney problems
  • A rare condition called diabetes insipidus, which affects the body’s ability to process water. This is a much less likely cause.

Symptoms of high sodium levels in the blood can include:

  • Headache
  • Nausea and vomiting
  • Lethargy
  • Confusion
  • Seizures
  • Loss of consciousness / coma.

Further reading

8 signs of dehydration – Know your risk – AXA PPP

Getting your salt intake right - AXA PPP

Dehydration - NHS factsheet