Sodium blood test
In short
A typical adult sodium result is 135 to 145 mmol/L. A high sodium most often means the body is short of water. Small rises are common in heat or during illness. Always read your result against the range printed on your own report.
A mineral salt (electrolyte) that keeps the body's water in balance.
Sodium keeps the right amount of water inside and outside your cells. It also helps nerves and muscles work. Most changes in sodium reflect how much water the body holds, not how much salt you eat.
Is my Sodium high or low?
Type your result to see where it sits.
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Typical range
| For | Range | Unit |
|---|---|---|
| Adults | 135–145 | mmol/L |
Typical ranges for adults. Labs differ a little, so the range printed next to your result is the one to go by.
If your Sodium is high
A high sodium most often means the body is short of water. Small rises are common in heat or during illness.
Common reasons
- Not drinking enough, especially in heat or during illness
- Losing fluid through heavy sweating or diarrhea
- Some medicines, including steroid medicines and laxatives
- Older age, when the sense of thirst is weaker
- Less often: a hormone problem that makes the kidneys lose too much water
If your Sodium is low
A low sodium most often means the body is holding extra water. Mild lows are common with some medicines and illnesses.
Common reasons
- Some medicines, especially water pills (diuretics) and some antidepressants
- Drinking a lot of water in a short time
- Vomiting or diarrhea
- Very high blood sugar, which draws water into the blood
- Less often: heart, liver or kidney conditions that make the body hold fluid
- Less often: low thyroid hormone or other hormone problems
What can throw it off
Very high blood sugar lowers sodium on the report, so doctors read the two together.
When it can’t wait
A Sodium of 160 mmol/L or more, or 120 mmol/L or less, usually needs a doctor's attention the same day. Call your doctor’s office, or their after-hours line. If you feel very unwell, call your local emergency number.
Questions to take to your appointment
- 1Could my medicines or how much I drink explain this?
- 2How far off is it, and should it be repeated soon?
- 3Should my blood sugar or thyroid be checked too?
Read together with
Doctors rarely read Sodium alone. These usually sit next to it.
- PotassiumA mineral salt (electrolyte) that keeps your heartbeat and muscles steady.
- ChlorideA mineral salt (electrolyte) that works with sodium to balance fluids.
- CO2Mostly bicarbonate, which keeps your blood from becoming too acidic.
- GlucoseThe sugar in your blood, your body's main fuel.
- CreatinineA waste product from muscles that the kidneys clear.
Quick answers
What is the sodium blood test?
Sodium: A mineral salt (electrolyte) that keeps the body's water in balance. Sodium keeps the right amount of water inside and outside your cells. It also helps nerves and muscles work. Most changes in sodium reflect how much water the body holds, not how much salt you eat.
What is a normal sodium level?
For most adults, sodium is typically 135 to 145 mmol/L. Labs differ a little, so the range printed next to your result is the one to go by.
What does a high sodium mean?
A high sodium most often means the body is short of water. Small rises are common in heat or during illness. Common reasons include not drinking enough, especially in heat or during illness; losing fluid through heavy sweating or diarrhea; some medicines, including steroid medicines and laxatives; and older age, when the sense of thirst is weaker. A doctor reads it together with your other results and how you feel.
What does a low sodium mean?
A low sodium most often means the body is holding extra water. Mild lows are common with some medicines and illnesses. Common reasons include some medicines, especially water pills (diuretics) and some antidepressants; drinking a lot of water in a short time; vomiting or diarrhea; and very high blood sugar, which draws water into the blood.
What can affect my sodium result?
Very high blood sugar lowers sodium on the report, so doctors read the two together.
When is my sodium result urgent?
A sodium result of 160 mmol/L or more, or 120 mmol/L or less usually needs a doctor's attention the same day. Call your doctor's office or their after-hours line. If you feel very unwell, call your local emergency number.
What should I ask my doctor about my sodium?
Questions worth taking to the appointment: Could my medicines or how much I drink explain this? How far off is it, and should it be repeated soon? Should my blood sugar or thyroid be checked too?
What this page can’t do
It reads each number on its own.
Doctors read results together — ALT with AST, ferritin with hemoglobin, TSH with free T4. A pattern says more than any single flag.
It doesn't know you.
Your age, your medicines, how you feel and your last result all change what a number means.
It doesn't remember.
Close this page and your results are gone. That's on purpose: nothing was ever sent to us.
We also make Vita: Health Coach, an app for those parts. It reads your whole report with your medicines and history in mind, answers follow-up questions in plain words, and keeps your reports in one place — for you and for the people you look after.
Vita: Health Coach on the App StoreSources
- MedlinePlus — Sodium blood test
- Mayo Clinic Laboratories — Critical values / critical results list
- University of Iowa Health Care — Critical laboratory values
Stuck on a word? See the medical words. How we choose our sources. More about Vita Health Coach.