Blood test
Lactate Blood Test
A lactate blood test measures lactic acid, which rises when tissues are short of oxygen, used mainly to assess seriously unwell patients.
Quick answer
Lactate Blood Test: what it is and what the results mean
Lactate (lactic acid) is produced when the body makes energy without enough oxygen. A blood test measures its level, which reflects how well tissues are being supplied with oxygen and blood.
- Why it is done: It is used in acutely unwell people to assess the severity of conditions such as sepsis, shock or poor circulation, to guide treatment, and to monitor response.
- Understanding results: A raised lactate suggests tissues are not getting enough oxygen or the body is under significant stress, and higher levels indicate more serious illness.
What it is
Lactate (lactic acid) is produced when the body makes energy without enough oxygen. A blood test measures its level, which reflects how well tissues are being supplied with oxygen and blood.
Why it is done
It is used in acutely unwell people to assess the severity of conditions such as sepsis, shock or poor circulation, to guide treatment, and to monitor response. It can also help investigate certain metabolic problems.
What to expect
It is taken from a vein or artery, sometimes as part of a blood gas sample. In emergencies it is often measured quickly at the bedside, with results available within minutes.
Understanding the results
A raised lactate suggests tissues are not getting enough oxygen or the body is under significant stress, and higher levels indicate more serious illness. A falling lactate with treatment is a good sign of improvement.
Good to know
Risks and limitations
The blood test is safe. Lactate can rise for several reasons, including vigorous muscle activity, so it is interpreted alongside the clinical picture and other tests, particularly in emergency care.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Lactate Blood Test: frequently asked questions
Why is lactate measured in sepsis?
A raised lactate in sepsis indicates that tissues are not receiving enough oxygen and helps judge how severe the illness is. Tracking it during treatment shows whether the patient is responding.
Does exercise affect lactate?
Yes. Intense muscle activity produces lactate, so vigorous exercise can raise it temporarily. In clinical settings this is taken into account when interpreting the result.
Related tests
Other blood test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- Association for Laboratory Medicine / relevant professional body
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