Why Lactate Rises
Lactate is produced when cells switch to anaerobic (without oxygen) metabolism. This happens during intense exercise (normal, temporary) or when tissues aren't getting enough oxygen due to illness — sepsis, shock, severe blood loss, or certain medication toxicity.Clinical Significance of Lactate Levels
| Level (mmol/L) | Significance |
|---|---|
| 0.5-1.0 | Normal |
| 1-2 | Mildly elevated — may reflect stress, mild illness, or recent exercise |
| 2-4 | Significant — associated with tissue hypoperfusion; a marker of illness severity in sepsis |
| >4 | Severe — indicates septic shock or severe tissue hypoxia; associated with higher mortality |
Uses in Emergency Medicine
- Sepsis severity assessment and monitoring response to treatment
- Assessing shock of any cause (haemorrhage, cardiogenic, septic)
- Monitoring during major surgery or trauma
- Diagnosing bowel ischaemia (very high lactate)
- Metformin-associated lactic acidosis (rare, serious complication)
Lactate ClearanceIn sepsis management, doctors track how quickly lactate falls with treatment ('lactate clearance') as a marker of treatment success — a falling lactate over hours is a good prognostic sign, while a persistently high or rising lactate signals ongoing severe illness.
Why does my muscle burn during intense exercise — is that lactate?
The 'burn' during intense exercise was traditionally attributed to lactate buildup, though the science is more complex (involving hydrogen ions and other factors). Blood lactate does rise significantly during anaerobic exercise and is used in sports science to assess fitness thresholds.
Is a high lactate always serious?
In a hospital emergency setting, yes, it's an important marker of illness severity. However, temporary elevation after a seizure, intense exercise, or a tourniquet during blood draw can cause a falsely elevated reading.
Can metformin cause high lactate?
Rarely, in the context of severe kidney impairment or acute illness, metformin can accumulate and contribute to lactic acidosis — this is why metformin is stopped during acute illness, dehydration, or before contrast dye procedures.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.