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Serum/plasma sodium-potassium ratio (or potassium concentration)

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

This test measures the relationship between sodium and potassium levels in your blood, often checked when electrolyte balance is suspected.

Quick summary

["Understanding your sodium-to-potassium balance helps identify imbalances that may affect heart function or fluid retention."]

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

Key facts at a glance

LOINC
28003-2
Short code
Sodium/Potassium SerPl-sRto
Synonyms
Sodium/Potassium SerPl-sRto
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 This Test Is Done

Your healthcare provider may order this test if you have symptoms like muscle weakness, irregular heartbeat, confusion, or signs of dehydration or fluid overload. It can also be part of routine monitoring for conditions like kidney disease, heart failure, or certain medications that affect electrolytes.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if sodium or potassium levels are being measured separately. Bring any medications you’re taking to your appointment.

How the Test Works

Blood is drawn from a vein (usually in your arm) and sent to a lab. The test measures sodium and potassium levels, then calculates their ratio or individual concentrations using standard lab methods.

What the Results Mean

Results help determine if your body is retaining or losing too much sodium or potassium. Abnormal levels may require adjustments to diet, medications, or further testing.

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

Frequently asked questions

What causes sodium-potassium imbalance to be tested?
Common triggers include symptoms like dizziness, rapid heartbeat, or unexplained fatigue, as well as conditions like heart disease, kidney problems, or certain medications (e.g., diuretics, ACE inhibitors).
How long does it take to get results?
Results are typically available within 1–2 business days, depending on your lab. Follow-up with your provider if you have concerns.
Can diet affect this test?
Yes—high sodium intake (e.g., processed foods) or potassium-rich foods (e.g., bananas, spinach) may influence results. Avoid extreme dietary changes before testing unless instructed by your doctor.
  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