Reading a lab report

  • The reference range is where results fall for 95 out of 100 healthy people. So 1 healthy person in 20 has a result just outside the range on any single test.
  • A slightly abnormal result is often repeated before anything is decided. Trends over time matter more than one number.
  • Results are read together with your symptoms, examination and medicines. A doctor may be unworried by a flagged result, or concerned by a "normal" one.
  • Dehydration, a recent meal, exercise, pregnancy, time of day and how long the sample took to reach the lab can all shift results.

Adult reference ranges used

For students & clinicians (technical detail)
  • eGFR: CKD-EPI 2021 creatinine equation (race-free): 142 × min(Scr/κ, 1) to the power α × max(Scr/κ, 1) to the power −1.200 × 0.9938 to the power of age × 1.012 if female; κ = 0.7 (female) or 0.9 (male), α = −0.241 (female) or −0.302 (male), Scr in mg/dL. Staged G1 to G5 per KDIGO.
  • Corrected calcium: measured calcium (mmol/L) + 0.02 × (40 − albumin g/L).
  • Anion gap: Na − (Cl + HCO₃), normal about 8 to 16 mmol/L. Raised gap with low bicarbonate suggests a high anion gap metabolic acidosis (ketoacidosis, lactate, kidney failure, toxins).
  • Non-HDL cholesterol: total cholesterol − HDL.
  • HbA1c: mmol/mol = 10.929 × (% − 2.15).
  • Unit factors: glucose 18.02; creatinine 88.4; urea to BUN 2.8; calcium 4.008; magnesium 2.431; phosphate 3.097; bilirubin 17.1; cholesterol 38.67; triglycerides 88.57; uric acid 59.48; free T4 12.87.
  • Critical-value flags here are common examples; each laboratory sets its own call-back limits.