TheCardiovascular
Reference values

Common laboratory tests

Reference ranges for the tests that are ordered most often, together with the pitfalls that make a value within the range wrong all the same.

Contents (7)

Reference ranges are statistical: by definition they encompass 95 % of a healthy reference population, which means that one healthy value in twenty falls outside them. Order twelve tests in a healthy person and the probability is around 46 % that at least one will fall outside.

The ranges below are guide values for adults. The method and the laboratory determine the range — always use the range printed on your own report.

Haematology

Full blood count, adults Haemoglobin, women 117–153 g/L Haemoglobin, men 134–170 g/L White cell count 3.5–8.8 ×10⁹/L Platelets 165–387 ×10⁹/L MCV 82–98 fL Neutrophils 1.6–5.9 ×10⁹/L Ranges according to NORIP and Swedish practice. Pregnant women and children have ranges of their own.
Test Reference Comment
Reticulocytes 20–100 ×10⁹/L Distinguishes a production defect from haemolysis or bleeding
Ferritin 15–300 µg/L (women 10–150) An acute phase protein — a normal ferritin does not exclude iron deficiency in the presence of inflammation
Transferrin saturation 15–50 % < 15 % indicates iron deficiency whatever the ferritin
Vitamin B12 150–650 pmol/L Grey zone 150–250: add homocysteine or methylmalonic acid
Folate > 7 nmol/L

Electrolytes and renal function

Electrolytes and renal function Sodium 137–145 mmol/L Potassium 3.5–4.4 mmol/L Calcium, ionised 1.15–1.33 mmol/L Magnesium 0.7–0.99 mmol/L Creatinine, women 45–90 µmol/L Creatinine, men 60–105 µmol/L Serum potassium is 0.2–0.5 mmol/L higher than plasma potassium; haemolysis gives a falsely high value.

See the renal parameters for the eGFR stages and albuminuria.

Inflammation and infection

Test Reference Comment
CRP < 3 mg/L Rises within 6–8 h, half-life about 19 h
ESR Women < 20, men < 15 mm/h Rises slowly; raised by anaemia, age and pregnancy
Procalcitonin < 0.25 µg/L Supports a bacterial aetiology; used to guide antibiotic therapy

Glucose and lipids

Test Threshold Comment
Fasting plasma glucose 4.0–6.0 mmol/L ≥ 7.0 on two occasions establishes a diagnosis of diabetes
HbA1c < 42 mmol/mol 42–47 = prediabetes; ≥ 48 = diabetes
Total cholesterol < 5.0 mmol/L Targets are governed by the total risk, not by the reference range
LDL < 3.0 mmol/L Target < 1.4 at very high risk
HDL Women > 1.3, men > 1.0 mmol/L
Triglycerides < 1.7 mmol/L > 10 carries a risk of pancreatitis

Cardiac markers and coagulation

Test Reference Comment
High-sensitivity troponin T < 14 ng/L The decision thresholds are assay-specific — follow the local 0/1-hour protocol
NT-proBNP < 125 ng/L (< 300 in acute dyspnoea) A normal value effectively excludes heart failure
D-dimer < 0.5 mg/L FEU Age-adjusted threshold: age × 0.01 above 50 years
INR 0.9–1.2
APTT 28–40 s
Fibrinogen 2–4 g/L An acute phase protein

Thyroid

Test Reference
TSH 0.4–4.0 mIU/L
Free T4 12–22 pmol/L
Free T3 3.1–6.8 pmol/L

TSH is logarithmically related to T4 — a small change in T4 produces a large change in TSH. During acute illness the TSH can be falsely low or high in the absence of thyroid disease; repeat it once the patient has recovered.

Pitfalls

  • Haemolysis raises the potassium, LDH and AST and lowers the haptoglobin.
  • A tourniquet left on during sampling raises the potassium, calcium and proteins.
  • Fasting is required for triglycerides but not for cholesterol, nor for glucose when the diagnosis is based on HbA1c.
  • Albumin affects the total calcium — use the ionised calcium or correct for albumin.
  • Biotin supplements interfere with many immunoassays, including troponin and TSH.

Authors

EBM AI
Evidensbaserad AI-agent

Updated August 19, 2026

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