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Sodium (Serum) Concentration

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of sodium, a key mineral, in your blood serum. Sodium helps balance fluids and maintain proper cell function.

Quick summary

["Your blood sodium level helps doctors check for dehydration, kidney issues, or other health concerns."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
32553-0
Short code
Sodium ?Tm sub Ur Qn
Synonyms
Sodium ?Tm sub Ur Qn
Category
electrolyte
Sample
urine
Container
Sterile urine container
Units
N/A
Ref low
136
Ref high
145
Critical range
120 N/A – 160 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84295
SNOMED
110741000
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Doctors may order a serum sodium test to diagnose or monitor conditions like dehydration, high blood pressure, kidney disease, or hormonal imbalances. It can also help assess how well your body is retaining or losing fluids.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein to draw blood. If you’re on a fluid-restricted diet, follow your doctor’s instructions carefully.

What the Results Mean

Results are typically reported in milliequivalents per liter (mEq/L). Abnormally low or high levels may signal underlying health issues that require further medical evaluation.

Common Conditions Affecting Sodium Levels

Low sodium (hyponatremia) can cause headaches, confusion, or muscle cramps, while high sodium (hypernatremia) may lead to thirst, fatigue, or irregular heartbeat. Both conditions can stem from fluid loss, kidney problems, or certain medications.

Reference range

Adult: 136-145 mmol/LN/A

Specimen: urine

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Sodium

Frequently asked questions

What causes my sodium level to be checked regularly?
Your doctor may check sodium levels if you have symptoms like excessive thirst, confusion, swelling, or if you’re on medications that affect fluid balance, such as diuretics or steroids.
How long does it take to get my sodium test results?
Results are usually available within 1–3 business days, depending on your lab. Follow-up with your healthcare provider if you have questions about your results.
Can I eat or drink anything before this test?
For most sodium tests, you can eat and drink normally unless instructed otherwise by your doctor. If you’re on a fluid-restricted diet, ask your provider for specific guidelines.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy