Lactate blood test: what to know

Cells make lactate when energy production changes, especially when tissues are not receiving or using oxygen efficiently. A result is interpreted alongside symptoms, examination findings, other blood tests, medicines, exercise, and how the sample was collected. A raised result does not identify one disease by itself. Serious infection, reduced blood flow, liver or kidney problems, intense exertion, some medicines, and metabolic disturbances can all affect lactate. Anaemia and several infections may cause symptoms that prompt wider testing, but the lactate result alone cannot diagnose them.

Follow the laboratory instructions about food, drink, exercise, and medicines; do not stop a prescribed medicine unless the ordering clinician tells you to. Tell the team about recent strenuous activity, symptoms, and any treatment you have received. The sample may be taken from a vein or, in some settings, another blood site. Keep the puncture area clean and apply pressure afterward if it oozes. Your clinician will interpret the result with the reason for testing and decide whether repeat testing or other investigations are needed.

Get urgent medical help for confusion, severe breathlessness, fainting, cold or mottled skin, severe weakness, persistent vomiting, or rapidly worsening illness. Fever with a very fast heart rate, new severe pain, or reduced urine output also warrants prompt assessment. Do not wait for a routine result if you feel acutely unwell. Conditions such as chronic kidney disease, severe infection, or major fluid loss can require immediate treatment, and the blood test is only one part of that assessment.

Why was lactate requested for me? Do I need to prepare in a particular way? Could exercise, medicines, or the blood draw affect the result? When will it be reviewed, and what further tests might be needed?