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Lactate in two units: the short answer
To convert lactate from mg/dL to mmol/L, multiply by 0.111. To go back from mmol/L to mg/dL, multiply by 9.009 (or divide by 0.111). For example, 20 mg/dL × 0.111 = 2.2 mmol/L. The converter above works in both directions and shows where the result sits against typical reference ranges.
What the test measures
Lactate (lactic acid) is reported in mg/dL in some US labs and in mmol/L almost everywhere else, including most emergency departments. Lactate's molar mass is 90.08 g/mol, so 1 mg/dL = 0.111 mmol/L and 1 mmol/L = 9.01 mg/dL.
Why the units differ
Sepsis guidance uses mmol/L: a lactate of 2 mmol/L (18 mg/dL) or more is raised, and 4 mmol/L (36 mg/dL) or more is a marker of high risk. Converting avoids mistakes when a report uses mg/dL.
Where the factor comes from
The conversion factor comes from the molar mass (90.08 g/mol) and the volume units on each side. Laboratories may round the factor slightly differently, which can change the last digit but never the clinical meaning.
How to convert step by step
- Check the unit printed next to the result on your report – mg/dL or mmol/L.
- mg/dL → mmol/L: multiply by 0.111.
- mmol/L → mg/dL: multiply by 9.009.
- Round to the same number of decimals your lab uses.
Worked example in reverse: 1.1 mmol/L × 9.009 = 9.9 mg/dL.
Lactate conversion chart
| mg/dL | mmol/L |
|---|---|
| 5 | 0.6 |
| 9 | 1 |
| 10 | 1.1 |
| 15 | 1.7 |
| 18 | 2 |
| 20 | 2.2 |
| 27 | 3 |
| 36 | 4 |
| 45 | 5 |
| 60 | 6.7 |
| 90 | 10 |
| mmol/L | mg/dL |
|---|---|
| 0.6 | 5.4 |
| 1 | 9 |
| 1.1 | 9.9 |
| 1.7 | 15.3 |
| 2 | 18 |
| 2.2 | 19.8 |
| 3 | 27 |
| 4 | 36 |
| 5 | 45 |
| 6.7 | 60.4 |
| 10 | 90.1 |
Lactate levels: what the numbers mean
| Category | mg/dL | mmol/L |
|---|---|---|
| Typical resting rangeAbout 0.5–2.2 mmol/L | 4.5 – 19.8 | 0.5 – 2.2 |
| Markedly raised≥4 mmol/L | ≥ 36 | ≥ 4 |
Thresholds as used in sepsis care (Surviving Sepsis Campaign). Exercise and a tight tourniquet raise lactate briefly.
Thresholds as used in sepsis care (Surviving Sepsis Campaign). Exercise and a tight tourniquet raise lactate briefly.
Interpreting lactate results
Lactate rises when tissues are short of oxygen (shock, severe infection, heart failure), but also with seizures, hard exercise, liver failure, and some medicines such as metformin in rare cases. In hospital, the trend matters more than a single number: a falling lactate after treatment is reassuring. For athletes, 'lactate threshold' testing uses the same units but a completely different context.
A single result outside the reference range is common and often not significant on its own. Reference ranges are set so that about 1 in 20 healthy people fall outside them, and every laboratory sets its own limits for its method. Use the range printed on your report and discuss results with the clinician who ordered the test.
When to see a doctor
Contact your clinician if a result is flagged as abnormal and you have symptoms, if a value is far outside the range, or if results are changing over time. This page explains units; it cannot diagnose or replace medical advice.
Frequently asked questions
Is 2 mmol/L lactate high?
2 mmol/L (18 mg/dL) is at the upper edge of normal and is the level at which sepsis protocols consider lactate raised.
Does exercise raise lactate?
Yes. Hard exercise can push lactate well above 4 mmol/L for a short time; it clears within an hour or so after rest.
Can I use this converter for any lab?
Yes for the unit conversion, which is fixed by chemistry. Reference ranges differ between labs and methods, so compare your converted value with your own lab's range.