Lactate

Blood Gases · also called Lactic acid, Blood lactate

What it measures

Lactate is produced when cells rely on anaerobic metabolism or when its clearance is reduced. It is a key marker of tissue hypoperfusion, used to identify and follow sepsis and shock.

Specimen and preparation

Specimen: Arterial or venous whole blood (heparin) or fluoride-oxalate plasma
Tube: Gray top
Preparation: Avoid prolonged tourniquet and fist clenching; analyse within 15 minutes or place on ice.

Reference range

Group	Range
Venous or arterial, at rest	0.5–2.0 (4.5–18) mmol/L (mg/dL)

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

Septic shock and hypoperfusion
Seizures and intense exercise
Liver failure
Metformin toxicity
Tissue ischaemia (mesenteric)
Delayed analysis or prolonged tourniquet

Method

Enzymatic (lactate oxidase) amperometric sensor on blood gas analyser, or laboratory colorimetric assay

Good to know

A lactate ≥4 mmol/L in sepsis indicates high risk; serial measurement guides resuscitation. Sepsis-3 septic shock = vasopressors needed to keep MAP ≥65 mmHg plus lactate >2 mmol/L despite adequate fluid resuscitation.

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