Red Blood Cell Count

Measured in 10^6/uL

The number of red blood cells — the cells that carry oxygen — in a sample of blood, which is affected by hydration and rarely interpreted alone.

What it is

Red blood cells (RBCs) carry oxygen from your lungs to the rest of your body, and this test counts how many are in a set volume of blood. Because it's a concentration, it moves with how hydrated you are — being dehydrated can push it up, and extra fluid can dilute it down — and it's also influenced by altitude, sex, pregnancy, and smoking. Clinicians almost always read it alongside hemoglobin, hematocrit, and the red cell indices (MCV, MCH, MCHC, RDW) as one picture, so a single RBC value on its own says relatively little.

Typical range

  • Male4.5–5.9 10^6/uL
  • Female4.0–5.2 10^6/uL

Source · StatPearls (NCBI Bookshelf NBK604207) (2024)

Reference ranges vary between laboratories, and what is normal for you depends on your own history. Your own lab’s range is the one printed on your report.

Worth asking your clinician

  • How does my RBC count fit with my hemoglobin and hematocrit — do they tell a consistent story?
  • Could hydration, altitude, or anything else about the day of the draw have affected this result?
  • Is this a change from my past results, or has it been steady for me?