Sodium is the main salt in the fluid outside your cells. It controls fluid balance, blood pressure and nerve and muscle function.
- Normal range (adults)
- 135–145 mmol/L
- Sample
- Blood
- Fasting
- Not usually needed
- Also called
- Serum Sodium, Na, Na+, S.Sodium, Blood Sodium, Sodium Serum
Sodium normal range
| Group | mmol/LSame unit in all countries |
|---|---|
| Adults | 135–145 |
Ranges vary slightly between laboratories. The range printed on your own report is the one to go by.
Why is the Sodium test done?
It is part of the electrolyte panel, checked when someone is unwell, vomiting, confused or on certain medicines.
What does a high Sodium level mean?
High sodium (hypernatremia) usually means the body has lost more water than salt. It can cause thirst, confusion and weakness.
Common causes
- Dehydration from not drinking enough, fever, vomiting or diarrhoea
- Excessive sweating in hot weather
- Diabetes insipidus (rare)
Diet and lifestyle tips
- Drink water regularly, especially in hot weather and during illness
- Use oral rehydration solution for diarrhoea or vomiting
What does a low Sodium level mean?
Low sodium (hyponatremia) can cause headache, nausea, confusion and, when severe, seizures. It is common in older people.
Common causes
- Water pills (diuretics) and some antidepressants
- Drinking very large amounts of water
- Vomiting or diarrhoea
- Heart, liver or kidney failure
- Underactive thyroid or adrenal glands
Diet and lifestyle tips
- Do not drink excessive amounts of water
- Do not restrict salt severely unless your doctor advises
- Ask your doctor to review your medicines
When should you see a doctor?
Seek urgent care for sodium below 125 or above 155 mmol/L, or for confusion, severe headache or seizures.
Last updated
This page is for general education and is not a diagnosis. Normal ranges differ between laboratories, so always compare your result with the reference range printed on your own report, and discuss abnormal results with your doctor.