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Sodium concentration in serum/plasma

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

This test measures the amount of sodium, a key mineral, in your blood. Sodium helps balance fluids and maintain normal heart rhythm.

Quick summary

["Sodium levels help doctors check if you have too much or too little sodium in your blood."]

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

Key facts at a glance

LOINC
42570-2
Short code
Sodium SerPl-msCnc
Synonyms
Sodium SerPl-msCnc
Category
electrolyte
Sample
serum
Container
Red-top tube (SST)
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
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test to diagnose or monitor conditions like high blood pressure, dehydration, kidney problems, or heart issues. It can also help check for electrolyte imbalances that may affect how your body uses water and nutrients.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s done as part of a broader blood panel. Drink plenty of water the day before if you’re dehydrated.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. You may feel a small pinch, but it’s quick and shouldn’t cause significant discomfort. The blood sample is then sent to a lab for testing.

What Do the Results Mean?

Results are compared to a standard range for healthy adults, but exact numbers vary by lab. Low sodium (hyponatremia) can cause headaches, confusion, or muscle cramps, while high sodium (hypernatremia) may lead to thirst, fatigue, or irregular heartbeat.

Reference range

Adult: 136-145 mmol/LN/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Sodium Level

Frequently asked questions

How long does it take to get my sodium test results?
Results are typically available within 1–3 business days, depending on your lab and insurance. Follow-up with your doctor if you have concerns about your results.
Can I eat or drink anything before my sodium test?
Most sodium tests don’t require fasting, but check with your doctor or lab about any specific instructions. If fasting is needed, avoid caffeine or alcohol before the test.
What causes sodium levels to be too high or too low?
High sodium can result from dehydration, excessive salt intake, or kidney problems. Low sodium often occurs from excessive sweating, vomiting, or certain medications (like diuretics). Lifestyle factors and medical conditions also play a role.
  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