If you have ever tried to line up a US lab report against an international guideline, you have hit the mg/dL versus mmol/L wall. This is a practical, factor-by-factor how-to for the four conversions people look up most: glucose, cholesterol (and the rest of the lipid panel), triglycerides, and creatinine. Each section gives the exact factor, where it comes from, and worked examples in both directions. To convert any value without doing the arithmetic by hand, use our Lab Unit Converter, which shows the factor and molar mass behind every result. For the bigger picture of why two unit systems exist at all, see the pillar guide, Conventional vs SI Units in the Clinical Lab.
Where These Factors Come From
Every mass-to-molar conversion factor is just the substance's molar mass combined with the scaling between deciliters and liters. The rule is: amount of substance (moles) = mass (grams) ÷ molar mass (grams per mole). A conventional result in mg/dL is a mass per deciliter; converting to mmol/L (or µmol/L) folds in both the molar mass and the dL→L step, producing a single multiplier. Because each analyte has a different molar mass, each has a different factor. There is no universal number — that is the one rule to remember.
Glucose: Multiply by 0.0555
Glucose (C₆H₁₂O₆) has a molar mass of about 180.16 g/mol. The factor to convert mg/dL to mmol/L is 1 ÷ 18.0182 ≈ 0.0555. To go back the other way, from mmol/L to mg/dL, multiply by 18.0182.
- 100 mg/dL × 0.0555 = 5.55 mmol/L (a normal fasting glucose).
- 126 mg/dL × 0.0555 = 7.0 mmol/L (the diabetes diagnostic threshold — a clean round number in SI, which is not a coincidence).
- 7.2 mmol/L × 18.0182 = 130 mg/dL.
- 200 mg/dL × 0.0555 = 11.1 mmol/L.
A quick mental shortcut: to go from mg/dL to mmol/L, divide by 18; to go from mmol/L to mg/dL, multiply by 18. It is accurate to within a rounding error and fast at the bedside.
Total Cholesterol, HDL and LDL: Multiply by 0.02586
Cholesterol has a molar mass of about 386.65 g/mol, giving a mg/dL to mmol/L factor of 0.02586 (reverse: 38.67). Crucially, total cholesterol, HDL, and LDL all use the same factor, because they are all measured as the cholesterol molecule — only the fraction being reported differs.
- Total cholesterol 200 mg/dL × 0.02586 = 5.17 mmol/L (the classic "desirable below 5.2" cutoff).
- 240 mg/dL × 0.02586 = 6.21 mmol/L (the "high" threshold).
- LDL 100 mg/dL × 0.02586 = 2.59 mmol/L.
- HDL 40 mg/dL × 0.02586 = 1.03 mmol/L.
- 5.0 mmol/L × 38.67 = 193 mg/dL.
Because all three cholesterol measures share the factor, you can convert an entire lipid panel's cholesterol values with one multiplier — but triglycerides are the exception, as we will see next.
Triglycerides: Multiply by 0.01129
Triglyceride molecules are much larger and heavier than cholesterol, so they have a smaller factor. The standard mg/dL to mmol/L factor for triglycerides is 0.01129 (reverse: 88.57), based on a representative triglyceride molar mass of about 885 g/mol.
- 150 mg/dL × 0.01129 = 1.69 mmol/L (the upper end of normal).
- 200 mg/dL × 0.01129 = 2.26 mmol/L.
- 1.7 mmol/L × 88.57 = 151 mg/dL.
This is the most common lipid-panel mistake: using the cholesterol factor (0.02586) for triglycerides. It would roughly double the value and could turn a normal triglyceride into an apparently high one. Always switch factors when you reach the triglyceride line.
Creatinine: Multiply by 88.42 (and Watch the Micro-Scale)
Creatinine has a molar mass of 113.12 g/mol, but there is a twist: it is reported in micromoles per liter (µmol/L) in SI, not millimoles, because the concentrations are small. The factor to convert mg/dL to µmol/L is 88.42 (reverse: 0.0113).
- 1.0 mg/dL × 88.42 = 88 µmol/L (a typical normal value).
- 1.2 mg/dL × 88.42 = 106 µmol/L.
- 2.0 mg/dL × 88.42 = 177 µmol/L (a clearly elevated value suggesting reduced kidney function).
- 90 µmol/L × 0.0113 = 1.02 mg/dL.
The scale prefix is the trap here. If you read 88 µmol/L as 88 mmol/L you are off by a thousandfold. Creatinine, bilirubin, and uric acid all live in the micromolar range, so always confirm whether the report says µmol/L or mmol/L.
Why Diabetes Thresholds Look "Rounder" in SI
One reason SI values are worth learning is that many international guidelines are written natively in mmol/L, and their thresholds are chosen as clean SI numbers. The fasting glucose diagnostic cutoff for diabetes is 7.0 mmol/L, which happens to equal 126 mg/dL — an awkward number in conventional units but a tidy one in SI. Impaired fasting glucose spans 6.1 to 6.9 mmol/L (110–125 mg/dL in some guidelines, 100–125 in others). The two-hour post-load threshold for diabetes is 11.1 mmol/L (200 mg/dL). If you memorize the SI thresholds, converting an incoming mg/dL value and comparing it to the guideline becomes a one-step check. This is exactly the kind of cross-referencing where a converter earns its keep: you read a US glucose of 118 mg/dL, convert to 6.55 mmol/L, and immediately see it sits in the impaired-fasting-glucose band of an SI-based guideline.
A Worked Clinical Scenario
Imagine you are reviewing a patient's results from a laboratory that reports in SI units, but the treatment guideline you are applying is written in conventional units. The report lists: glucose 6.8 mmol/L, total cholesterol 5.4 mmol/L, LDL 3.2 mmol/L, triglycerides 2.1 mmol/L, creatinine 102 µmol/L. Converting each back to conventional units:
- Glucose: 6.8 × 18.0182 = 123 mg/dL — just below the 126 mg/dL diabetes threshold, in the prediabetes range.
- Total cholesterol: 5.4 × 38.67 = 209 mg/dL — borderline, above the 200 mg/dL desirable cutoff.
- LDL: 3.2 × 38.67 = 124 mg/dL — above the 100 mg/dL optimal target.
- Triglycerides: 2.1 × 88.57 = 186 mg/dL — above the 150 mg/dL normal limit (note we used the triglyceride factor, not the cholesterol one).
- Creatinine: 102 × 0.0113 = 1.15 mg/dL — within a typical adult range.
Notice how each analyte required its own factor, and how the triglyceride line would have been badly wrong if you had reused the cholesterol multiplier. This is the everyday reality of reading cross-border results, and it is why an analyte-aware converter removes a real source of error rather than just saving keystrokes.
Rounding, Precision, and Significant Figures
How many decimal places should a converted value carry? Match the precision of the original report and the clinical question. Glucose and cholesterol are usually meaningful to one decimal place in mmol/L; creatinine in µmol/L is typically reported as a whole number. The danger is rounding before a comparison: a glucose of 6.99 mmol/L rounded to 7.0 might read as diabetic when the underlying value is fractionally below the cutoff. Keep the extra digit until the final comparison, then round for reporting. When you use the converter, it preserves sensible precision automatically and shows the underlying factor so you can see whether a borderline value is truly over or under a threshold.
What About Urea, Uric Acid and Bilirubin?
The same molar-mass logic extends to the rest of the panel. Urea is reported as blood urea nitrogen (BUN) in mg/dL in the US and as urea in mmol/L elsewhere, with a factor of 0.357 (a BUN of 14 mg/dL is about 5.0 mmol/L urea). Uric acid converts from mg/dL to µmol/L at 59.48 (6.0 mg/dL ≈ 357 µmol/L). Bilirubin converts from mg/dL to µmol/L at 17.1 (1.0 mg/dL ≈ 17 µmol/L). Like creatinine, uric acid and bilirubin sit in the micromolar range, so the same prefix caution applies. The converter includes these alongside the headline four, so you can process an entire chemistry panel without switching tools or hunting for factors.
Quick Reference Table
The four workhorse conversions, plus the reverse multipliers:
- Glucose: mg/dL × 0.0555 = mmol/L; mmol/L × 18.0182 = mg/dL.
- Total cholesterol / HDL / LDL: mg/dL × 0.02586 = mmol/L; mmol/L × 38.67 = mg/dL.
- Triglycerides: mg/dL × 0.01129 = mmol/L; mmol/L × 88.57 = mg/dL.
- Creatinine: mg/dL × 88.42 = µmol/L; µmol/L × 0.0113 = mg/dL.
Common Mistakes to Avoid
- Using one factor for everything. Glucose, cholesterol, triglycerides, and creatinine each have their own factor. Reusing a factor across analytes is the number-one error.
- Applying the cholesterol factor to triglycerides. Triglycerides are heavier and use 0.01129, not 0.02586.
- Confusing µmol/L with mmol/L. Creatinine is micromolar; misreading the prefix is a 1000× error.
- Rounding too aggressively before comparing to a threshold. Near a diagnostic cutoff, keep a decimal place until the final step.
- Forgetting the reference range. A correct conversion still has to be interpreted against the reporting laboratory's own reference interval, which varies by method and population.
A Note on Safe Use
These factors are exact arithmetic, but a converted number is only as useful as the value you start with and the reference range you compare it against. Reference intervals differ between laboratories because they depend on the analytical method, instrument, and population. This article and the converter are educational and reference resources — not medical advice, and not a replacement for a validated laboratory report or clinical judgment. Always read a converted result against the reporting laboratory's own reference range, and involve a qualified clinician for decisions about care.
Convert It Instantly
Rather than memorize four factors and worry about micro- versus milli- prefixes, let the tool do it. Our Lab Unit Converter handles glucose, the full lipid panel, creatinine, and about 20 other analytes, converts in both directions, and displays the exact factor and molar mass it used so you can check the math. Everything runs in your browser — nothing you type is ever uploaded. For the wider story of why labs use different unit systems in the first place, read the companion pillar, Conventional vs SI Units in the Clinical Lab.