Sodium Blood Test Explained

What this test measures

• Sodium is an electrolyte that helps the body manage fluid balance, nerve signals, and muscle function.
• A sodium result often reflects water balance as much as salt balance.
• Doctors commonly review sodium with kidney tests, medicines, recent illness, and symptoms.

Typical reference range

• Sodium is often reported around 135 to 145 mmol/L in adults.

Reference ranges can vary slightly by lab, and interpretation depends on symptoms, hydration, medicines, and how quickly the level changed. This checker treats about 135 to 145 mmol/L as a simplified adult educational band.

Enter your value

This check is for quick educational context only. It is not stored as a medical record and does not replace clinical interpretation. Always compare your result with the reference range printed on your own lab report.

Low / Normal / High context

Low

• Low sodium may be associated with excess water relative to sodium, vomiting, diarrhea, some medicines, hormone-related factors, or fluid-balance conditions.
• How low the number is and whether symptoms are present often matters as much as the cause itself.

Normal

• A normal sodium result often suggests water and sodium balance are within the expected range at the time of testing.
• Doctors may still compare it with symptoms, recent illness, medicines, and kidney markers if there are ongoing concerns.

High

• High sodium is often associated with dehydration, water loss, fever, diarrhea, or reduced access to fluids.
• It usually reflects a water-balance problem rather than salt intake alone.

How this marker is interpreted with other tests

• Creatinine and eGFR can add kidney context when fluid balance or clearance is being reviewed.
• Urea may help add context when dehydration is part of the question.
• Doctors also consider symptoms, blood pressure, medicines such as diuretics, and recent vomiting or diarrhea.

What to discuss with your doctor

• Whether the result is only slightly outside range or clearly abnormal.
• Whether dehydration, fluid overload, or medicines could explain the change.
• Whether kidney tests or repeat electrolytes would add context.
• Whether your symptoms make the result more urgent to review.

When to seek urgent care

• Seek urgent care if you have confusion, seizures, severe sleepiness, fainting, severe vomiting, severe weakness, or signs of severe dehydration.

Related markers

Theme hubs help you move from one marker page into the wider group that doctors often review alongside it. If you have several numbers from the same group, you can enter them together there.

FAQ

References

• MedlinePlus: Sodium blood test
• Cleveland Clinic: Hyponatremia
• Cleveland Clinic: Hypernatremia