High blood sodium

Clinically: Hypernatraemia · also high sodium, raised sodium, high blood sodium

electrolyte

This describes what this condition typically looks like. It is not a diagnosis and cannot tell you whether you have it -- patterns overlap, results vary between labs, and the same numbers mean different things in different people. Diagnosis usually rests on Sodium, interpreted alongside symptoms and history rather than read off a report.

unverified These explanations are written to be easy to read and have not yet been checked against a source. The ranges and measurement notes on this page show theirs.

definition unverified

Sodium in the blood is above normal. Usually the body has lost too much water, or has not had enough to drink.

Serum sodium concentration above 145 mmol/L, reflecting serum hyperosmolality; sodium above 160 mmol/L is severe hypernatraemia. It usually results from a deficit of water relative to body sodium, from a defect in urine concentration or insufficient water intake.

caveats unverified

Older adults are more at risk, because thirst gets weaker with age. Early signs are vague, such as tiredness and weakness. A falsely high result can happen when blood protein or fat levels are low.

No clinical version written yet.

The typical lab pattern

What the diagnosis rests on

The results a diagnosis is actually made on.

Sodium

high

—

Defined as serum sodium above 145 mmol/L; above 160 mmol/L is severe. A falsely high sodium can occur when blood protein or fat is low, and should be ruled out first.

Consistent with it

Fits the picture, but not enough on its own.

Urea nitrogen	high	—	Part of the standard work-up. A high urea nitrogen, especially with a high urea-to-creatinine ratio, points to dehydration as the cause.
Creatinine	high	—	Part of the standard work-up. A raised creatinine can point to dehydration as the cause.
Glucose	high	ref ≤ 99	High blood glucose changes how sodium should be read, so sodium is corrected for glucose. High glucose can also cause water loss through the urine.
Potassium	low	—	Checked as part of the work-up. Low potassium (below 3.0 mmol/L) can stop the kidneys concentrating urine, leading to water loss.
Calcium, total	high	—	Checked as part of the work-up. High calcium (above 11 mg/dL) can stop the kidneys concentrating urine, leading to water loss.

How it usually feels

Feeling sick to your stomach · occasional
Feeling thirsty all the time · common
Losing weight without trying · occasional
Muscles feeling weak · common
Trouble thinking clearly · occasional

Frequencies say how often a symptom accompanies this condition — not the other way round. Most people with any of these symptoms do not have this.