Normal values and thresholds

Electrolytes and kidneys

These are the Australasian harmonised adult ranges, used by most Australian laboratories.

• Sodium: 135 to 145 mmol/L.
• Potassium: 3.5 to 5.2 mmol/L.
• Chloride: 95 to 110 mmol/L.
• Bicarbonate: 22 to 32 mmol/L.
• Creatinine: men 60 to 110 µmol/L, women 45 to 90 µmol/L (adults up to 60).
• Calcium (albumin adjusted): 2.10 to 2.60 mmol/L.
• Phosphate: 0.75 to 1.50 mmol/L.
• Magnesium: 0.70 to 1.10 mmol/L.
• Alkaline phosphatase: 30 to 110 U/L. Total protein: 60 to 80 g/L.
• Anion gap: about 8 to 16 mmol/L.

Full blood count

Typical ranges; laboratories differ a little.

• Haemoglobin: about 130 to 180 g/L in men, 115 to 165 g/L in women.
• White cells: 4.0 to 11.0 x 10^9/L.
• Platelets: 150 to 400 x 10^9/L.
• MCV: 80 to 100 fL.
• Iron deficiency: ferritin below 30 µg/L, or up to about 70 µg/L with inflammation; transferrin saturation below 20%.
• Haemochromatosis: transferrin saturation above 45% with a high ferritin.
• Neutropenic fever: 38 degrees or more with neutrophils below 0.5 x 10^9/L.

Blood gases

Arterial, breathing room air.

• pH: 7.35 to 7.45.
• PaCO2: 35 to 45 mmHg.
• PaO2: 80 to 100 mmHg, lower in older people.
• Bicarbonate: 22 to 26 mmol/L.
• Lactate: above 2 mmol/L is abnormal.
• Winter's formula: expected PaCO2 = 1.5 x bicarbonate + 8, plus or minus 2.

Glucose and diabetes

• Diabetes: HbA1c 48 mmol/mol (6.5%) or more; fasting glucose 7.0 mmol/L or more; 2-hour or random glucose 11.1 mmol/L or more.
• Hypoglycaemia: below 4.0 mmol/L. Driving on insulin: not below 5 mmol/L.
• DKA: ketones 3.0 mmol/L or more, with pH below 7.3 or bicarbonate below 15.
• Gestational diabetes (2025 thresholds): fasting 5.3, 1 hour 10.6, 2 hours 9.0 mmol/L.

Kidneys

• AKI: creatinine up 26.5 µmol/L in 48 hours, or 1.5 times baseline within 7 days, or urine under 0.5 mL/kg/h for 6 hours.
• CKD: eGFR under 60, or another kidney abnormality, for at least 3 months.
• Albuminuria (urine ACR): A1 under 3, A2 3 to 30, A3 above 30 mg/mmol.

Heart and lipids

• NT-proBNP below 300 pg/mL makes acute heart failure unlikely.
• LDL targets: below 1.4 mmol/L after ACS, with a 50% fall; below 1.8 mmol/L after ischaemic stroke.
• Familial hypercholesterolaemia: suspect when adult LDL is 5 mmol/L or more.
• Treat regardless of calculated risk: total cholesterol above 7.5 mmol/L, or blood pressure above 160/100.
• Triglycerides above 10 mmol/L carry a risk of pancreatitis.

Drug levels and monitoring

• INR: 2 to 3 for AF and venous thromboembolism; 2.5 to 3.5 for a mechanical mitral valve.
• Lithium: taken 12 hours after the dose; maintenance 0.6 to 0.8 mmol/L; toxicity usually above 1.5.
• TSH: recheck about 6 weeks after a thyroxine dose change.
• Urate target on allopurinol: below 0.36 mmol/L, below 0.30 with tophi.

Fluids and other samples

• Ascitic fluid: neutrophils above 250 per cubic millimetre mean spontaneous bacterial peritonitis.
• Pleural fluid: exudate if protein ratio above 0.5, LDH ratio above 0.6, or fluid LDH above two thirds of the upper limit of serum LDH. pH below 7.2 in a parapneumonic effusion: drain it.
• Synovial fluid: white cells often above 50 x 10^9/L in septic arthritis.

Babies and pregnancy

• CTG: baseline 110 to 160 beats a minute; variability 6 to 25.
• Newborn jaundice: conjugated bilirubin over 35 µmol/L, or over 20% of the total, is urgent.
• Fetal scalp sample: lactate 4.8 or more, or pH 7.20 or less: expedite birth.

Environment

• Lead: investigate a blood lead above 5 µg/dL.
• Noise: 85 dB(A) over 8 hours is the workplace limit; noise damage shows as a notch at 4 kHz.