Short answer: the electrolyte panel measures four salts dissolved in the blood: sodium, potassium, chloride and bicarbonate (often written CO2). They keep water balance, nerves, muscles, heart rhythm and blood acidity in order. For these four, mmol/L and mEq/L are the same number. A high potassium can come from the sample itself if blood cells broke in the tube (haemolysis), which is why laboratories flag it and doctors often repeat the test.
At a glance
| Measures | Sodium, potassium, chloride, bicarbonate in serum or plasma |
|---|---|
| Units | mmol/L = mEq/L for all four |
| LOINC | 2951-2 Na · 2823-3 K · 2075-0 Cl · 2028-9 CO2 (total) |
| Part of | The basic and comprehensive metabolic panels |
| Watch for | "Haemolysed" on the report, which can raise potassium |
| Keep | Values, units, ranges and date, with creatinine |
What each value is
- Sodium reflects water balance more than salt intake; thirst, kidneys and hormones keep it narrow.
- Potassium matters for muscles and heart rhythm; small changes are significant, and many medicines affect it.
- Chloride usually moves with sodium.
- Bicarbonate (total CO2) reflects the blood's acid–base balance; see acid–base balance.
Some reports add the anion gap, a calculation from these values (sodium minus chloride and bicarbonate) that helps doctors with acid–base questions.
How the results are written on the report
| Result on the report | LOINC code | Unit |
|---|---|---|
| Sodium, serum or plasma | 2951-2 | mmol/L (= mEq/L) |
| Potassium, serum or plasma | 2823-3 | mmol/L (= mEq/L) |
| Chloride, serum or plasma | 2075-0 | mmol/L (= mEq/L) |
| Carbon dioxide (bicarbonate), total | 2028-9 | mmol/L (= mEq/L) |
Why the sample can change potassium
Potassium is high inside blood cells. If cells break during or after the blood draw (a tight tourniquet, a long wait before the sample is spun, a difficult draw), potassium leaks out and the result reads high. Laboratories often note "haemolysed". Doctors usually repeat an unexpected high potassium before acting on it.
Keeping the results in your record
Electrolytes are read with kidney function and your medicines. Keep them with creatinine and eGFR in Anpheros Daily, where each value is charted over time, or chart one value with the free lab results tracker.
What this page does not do
It explains the panel. It does not interpret your results or advise on diet, fluids or medicines; abnormal electrolytes can need prompt medical attention, so follow your doctor's advice.
Sources
Frequently asked questions
Are mmol/L and mEq/L the same for electrolytes?
For sodium, potassium, chloride and bicarbonate, yes: each carries a single charge, so the numbers are identical.
Why was my potassium high and then normal?
A common reason is haemolysis: cells broke in the sample and released potassium. That is why doctors repeat an unexpected value.
Is CO2 on my report the gas I breathe out?
It is total carbon dioxide in the blood, almost all of it as bicarbonate. It reflects acid–base balance, not your breathing on the day.
Which medicines change electrolytes?
Many, including diuretics, some blood pressure medicines and laxatives. Bring your medication list to the appointment.
Try it in Anpheros Daily
Photograph your lab report and Anpheros Daily lines up each value with its reference range, so you can compare reports from different laboratories.
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