The MEQ medical abbreviation, usually written mEq, stands for milliequivalent, a unit used to measure electrolytes such as potassium, sodium, chloride and bicarbonate. It shows up in two main places: on lab reports as mEq/L, and on orders and labels for electrolyte supplements such as potassium chloride.
Electrolytes are minerals that carry an electric charge in body fluids. Their job depends on that charge more than on their weight, so clinicians count them in a unit that reflects charge. That unit is the milliequivalent, one thousandth of an equivalent.
At a glance
Stands for
MilliequivalentWritten as
mEq, MEQ, meq; per liter as mEq/LUsed for
Potassium, sodium, chloride, bicarbonate, some calcium and magnesium productsWhere you see it
Lab reports, IV fluid orders, potassium prescriptions, supplement labelsRelated unit
mmol (millimole), equal to mEq for single charge ionsDo not confuse with
mg (milligram), a unit of weight
What the MEQ medical abbreviation measures
An equivalent is a chemistry unit based on how much electric charge a substance carries when it dissolves. A milliequivalent is one thousandth of that. Using charge makes sense for electrolytes, because nerves, muscles and the heart respond to the balance of charged particles in and around cells.
For ions with a single charge, such as sodium, potassium and chloride, one milliequivalent equals one millimole, so the numbers match. For ions with a double charge, like calcium and magnesium, one millimole equals two milliequivalents. That is why some labs and countries report electrolytes in mmol/L and others in mEq/L, and why the two can look different for calcium even when they describe the same result.
mEq/L on a lab report
Basic and complete metabolic panels, written BMP and CMP, list several electrolytes in milliequivalents per liter of blood. Typical adult reference ranges are shown below as rough guides only.
| Electrolyte | Usual adult range, about |
|---|---|
| Sodium (Na) | 135 to 145 mEq/L |
| Potassium (K) | 3.5 to 5.0 mEq/L |
| Chloride (Cl) | 96 to 106 mEq/L |
| Bicarbonate (CO2 or HCO3) | 22 to 29 mEq/L |
Each lab sets its own range, printed beside your result, and that range is the one to compare against. A number slightly outside the range does not always mean a problem; your clinician reads it alongside your symptoms and other results.
mEq on prescriptions and IV orders
Potassium chloride is the medicine most patients see written in mEq. Tablets, powders and liquids are labeled by milliequivalents of potassium, such as 10 mEq or 20 mEq, rather than by milligrams. IV fluids can also carry added potassium, written as a number of mEq per liter of fluid.
Hospital order: "D5 1/2NS with 20 mEq KCl/L at 75 mL/hr." This means a dextrose and half strength saline fluid with 20 milliequivalents of potassium chloride in each liter, running IV, into a vein, at 75 milliliters an hour. It shows the format only.
Sodium bicarbonate, some magnesium products and certain calcium preparations may also be labeled in milliequivalents. On a home prescription, the label translates the order into plain steps.
mEq versus mg and mmol
Units that look alike can lead to large dose mistakes if they are swapped, so it helps to know what each one counts.
| Unit | What it counts | Where you see it |
|---|---|---|
| mEq | Electric charge | Potassium doses, US lab reports |
| mmol | Number of particles | Lab reports in many countries, phosphate products |
| mg | Weight | Most medicine strengths |
A potassium tablet labeled 20 mEq does not contain 20 mg of potassium. Mixing up these units on an order or during a home medication review can change the amount given many times over, which is why pharmacists double check them.
Why potassium in mEq gets extra care
Potassium is essential, but levels that run too high or too low can affect the heart rhythm. For that reason, concentrated IV potassium is treated as a high alert medicine in hospitals, with premixed bags, pump limits and independent double checks. By mouth, potassium tablets often come in extended release forms meant to go down whole unless directions say otherwise.
Many people on certain water pills take a potassium supplement in mEq, and their blood level is checked from time to time. Only the prescriber should adjust the amount, based on those lab results.
Questions to ask about an mEq dose
- Is my dose written in mEq or mg, and does the label match the prescription?
- Should the tablet be swallowed whole, or can it be split or dissolved?
- When will my potassium or sodium level be checked again?
- Do any of my other medicines raise or lower potassium?
Students can find more dosing and unit shorthand in the prescription abbreviations section, organized by what each term tells the person giving the medicine.
Lab ranges and doses on this page are general examples. Your own results and any electrolyte medicine you take should be reviewed with the clinician who ordered them.
Frequently asked questions
What does mEq mean on a prescription?
It means milliequivalent, the unit used to state the strength of electrolyte medicines like potassium chloride. A label might read 20 mEq, which refers to the amount of potassium in each dose.
What does mEq/L mean on lab results?
It means milliequivalents per liter, a measure of how much of an electrolyte is in a liter of blood. Sodium, potassium, chloride and bicarbonate are often reported this way in the United States.
Is mEq the same as mg?
No. Milligrams measure weight, while milliequivalents measure electric charge. The two numbers for the same product are different, so they should never be swapped.
Is mEq the same as mmol?
For sodium, potassium and chloride, which carry a single charge, the numbers are the same. For calcium and magnesium, which carry a double charge, one millimole equals two milliequivalents.