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Sodium concentration in serum measured over a 6-hour period

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

This test measures how much sodium your body loses or retains over six hours. Sodium is a key electrolyte that helps balance fluids and support nerve and muscle function.

Quick summary

["Assesses sodium balance and fluid shifts over time, useful in monitoring conditions like dehydration or kidney issues."]

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

Key facts at a glance

LOINC
18376-4
Short code
Sodium 6h Ur-sRate
Synonyms
Sodium 6h Ur-sRate
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?

Your healthcare provider may order this test if you have symptoms like excessive thirst, confusion, or unusual fatigue that could indicate fluid or electrolyte imbalances. It may also be used to monitor long-term sodium levels in people with chronic conditions like kidney disease or heart failure.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for a few hours before the blood draw, but this depends on your provider’s instructions. Bring any medications or supplements you’re taking to your appointment.

What Happens During the Test?

A healthcare professional will draw blood from a vein, typically in your arm. The process takes a few minutes, and you may feel a slight pinch. The blood sample is then sent to a lab for analysis over the specified period.

What the Results Mean

Results help determine whether your sodium levels are too high (hypernatremia) or too low (hyponatremia). Abnormal levels can affect your body’s ability to regulate fluids, leading to serious health issues if untreated.

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

6-Hour Sodium Rate (Serum)

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–3 business days, depending on lab processing times. Your provider will discuss the findings with you during your follow-up visit.
What causes abnormal sodium levels?
Abnormal sodium levels can result from dehydration, kidney problems, excessive salt intake, vomiting, diarrhea, or certain medications. Chronic conditions like heart failure or liver disease may also play a role.
Can I eat or drink anything before the test?
Follow your provider’s instructions, but generally, fasting for 4–8 hours before the blood draw is common. Avoid caffeine or alcohol in the hours leading up to the test if advised.
  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