Blood and lab tests
What Does Sodium Level Mean on a Blood Test?
Sodium level · say it: SO-dee-um LEV-ulAlso written: Na, Na+, serum sodium, blood sodium
Short answer
Your sodium level shows how much sodium is in your blood, which mostly reflects the balance between salt and water in your body.
What it means
Sodium is an electrolyte, a mineral that carries an electrical charge in body fluids. It helps control how much water is in and around your cells, and nerves and muscles need it to work. The kidneys, hormones and thirst work together to keep blood sodium within a narrow band.
Sodium is the first item on most electrolyte panels and on basic and comprehensive metabolic panels. A blood sodium result tells you more about water than about salt: a low level usually means there is too much water compared with sodium, and a high level usually means too little water. Doctors use it to check fluid balance, kidney function and the effects of medicines such as diuretics and some antidepressants. A low level is called hyponatremia; a high level is called hypernatremia.
Blood sodium is not the same as the sodium listed on a food label, and it does not track how salty your diet is from day to day.
Where you may see it
- Electrolyte panels, usually listed first as "Na"
- Basic and comprehensive metabolic panels
- Hospital blood results checked while someone is on IV fluids or diuretics
📄 How it looks on a report
Sodium 131 mmol/L L
🙅 What it does not mean
- A low blood sodium does not usually come from eating too little salt. Most often it reflects water balance, and the cause decides what your doctor suggests.
- A high sodium is not the same thing as high blood pressure from a salty diet. It most often points to the body being short of water.
- A small flag is not always a new problem. Medicines, a recent illness and drinking very large amounts of fluid can all shift the number.
🗒️ Questions to ask your doctor
🧾 Reports where you will see “Sodium level”
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💊 Medicines whose labels mention “Sodium level”
Plain-English explanations of each medicine, from its official FDA label.
- Amitriptyline
An antidepressant of the tricyclic type
- Duloxetine
A serotonin and norepinephrine reuptake inhibitor (SNRI) type of antidepressant medicine
- Escitalopram
a selective serotonin reuptake inhibitor (SSRI), a type of antidepressant
🔗 Read more from trusted sources
- “Sodium level” on MedlinePlus ↗
US National Library of Medicine
- MedlinePlus lab test guides ↗
US National Library of Medicine
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