How to read a blood count and electrolytes
Other platforms explain it with text and video. In VMS you practice it on the patient.
A lab value only means something next to the patient and the last result. Use your lab's own ranges; the ones below are typical adult values.
Step by step
Check the sample
Right patient, time and type of sample. A delayed or hemolyzed sample can raise potassium falsely. [1]
White blood cells
About 4.5 to 11 x10^3/µL. High: infection, inflammation, steroids. Low: infection risk. [1]
Hemoglobin and platelets
Hemoglobin roughly 12 to 16 g/dL in women and 13.5 to 17.5 in men; platelets 150 to 450 x10^3/µL. Low platelets raise bleeding risk. [1]
Sodium and potassium
Sodium 135 to 145 mEq/L; potassium 3.5 to 5.0 mEq/L. Abnormal potassium can cause dangerous heart rhythms. [2]
Kidney and glucose
Creatinine about 0.6 to 1.2 mg/dL, BUN 7 to 20 mg/dL, fasting glucose 70 to 99 mg/dL. [2]
Compare and trend
Look at the last results. A fast change matters more than a single value. [1]
Act on critical values
Report critical results right away, read back, and check the patient. [2]
Common errors
- Ignoring the trend.
- Treating a falsely high potassium from a hemolyzed sample.
- Using another lab's ranges.
Practice it in VMS
In VMS you do this on the patient, not on paper: every step goes on the checklist with a score, and in Teach mode Blocky tells you what comes next.
Sources
Facts and steps follow AAMC Core Entrustable Professional Activities (Core EPAs); NCSBN 2026 NCLEX-RN Test Plan. VMS is not affiliated with these organizations. Updated: 2026-10-11.