mg/dL to µmol/L Converter

Converting mg/dL to µmol/L

mg/dL (milligrams per decilitre) is a mass concentration: how many milligrams of a substance are in 100 mL of blood. µmol/L (micromoles per litre) is a molar concentration: how many micromoles – a count of molecules – are in a litre. US laboratories mostly report in mg/dL; laboratories in the UK, Europe, Australia, Canada and much of the world use SI units such as µmol/L and mmol/L.

Because the conversion depends on how heavy each molecule is, there is no single factor – each substance has its own. The general formula is:

µmol/L = mg/dL × 10,000 ÷ molar mass (g/mol)

mg/dL = µmol/L × molar mass ÷ 10,000

The factor of 10,000 comes from two steps: × 10 to go from per decilitre to per litre, and × 1,000 to go from milligrams per gram-per-mole (millimoles) to micromoles.

The converter above has three modes: mg/dL → µmol/L and µmol/L → mg/dL for twelve common substances, and a custom mode where you enter any molar mass.

Conversion factors for common tests

For glucose, cholesterol, calcium, magnesium, phosphorus, urea and lactate, results are normally reported in mmol/L rather than µmol/L – simply divide the µmol/L figure by 1,000. The converter shows both. For those substances, the mg/dL to mmol/L converter is often more convenient.

Creatinine: mg/dL to µmol/L

Creatinine is the most common reason people need this conversion, because it underpins kidney-function testing worldwide.

A typical adult reference interval is about 0.7–1.3 mg/dL (62–115 µmol/L) for men and 0.5–0.95 mg/dL (44–84 µmol/L) for women (MedlinePlus), though labs vary. For more detail on what a raised value means, see high creatinine; for a dedicated converter with reference ranges, see the creatinine converter. Remember that eGFR equations such as CKD-EPI use creatinine in mg/dL, so a µmol/L value must be divided by 88.4 first – the eGFR calculator accepts either unit.

Uric acid: mg/dL to µmol/L

Uric acid becomes less soluble above about 6.8 mg/dL (about 400 µmol/L) at body temperature, which is the threshold usually used to define hyperuricaemia. The NBME exam reference range is 3.0–8.2 mg/dL (0.18–0.48 mmol/L). See the uric acid converter for more.

Bilirubin: mg/dL to µmol/L

Total bilirubin is usually under about 1.0–1.2 mg/dL (17–21 µmol/L) in adults. Jaundice – yellowing of the eyes and skin – usually becomes noticeable only when bilirubin is well above the reference range. In newborns, bilirubin is plotted against age in hours on special charts, and both mg/dL and µmol/L are used depending on country. See the bilirubin converter.

Iron: µg/dL to µmol/L

Serum iron is reported in µg/dL (micrograms per decilitre) in the US, not mg/dL, so the factor is 1,000 times smaller: µmol/L = µg/dL × 0.179 (or ÷ 5.585).

TIBC uses the same factor. The NBME reference range for serum iron is 65–175 µg/dL in men (11.6–31.3 µmol/L) and 50–170 µg/dL in women (9.0–30.4 µmol/L). For the full iron panel, see the TIBC blood test page.

How to find a molar mass

If your substance is not in the list, use the custom mode with its molar mass (also called molecular weight). Reliable sources include the PubChem database, pharmacology references and the laboratory's own documentation. A few points:

• Use the molar mass of the form that is measured. For example, laboratory "phosphate" results are usually standardised to phosphorus (30.97 g/mol), not the phosphate ion (94.97 g/mol).
• For ions, use the mass of the ion itself (for example calcium 40.08 g/mol), not a salt.
• Hydrated salts (such as magnesium sulfate heptahydrate) have much larger molar masses than the anhydrous form – this matters for medicines, not for blood tests.
• Proteins and hormones are often reported in mass units or international units and may not have a simple molar conversion.

Converting a reference range

To convert a whole reference range, convert each limit separately with the same factor:

Small differences from published SI ranges (such as the NBME's 0.18–0.48 mmol/L for uric acid) come from rounding. When you compare your own result, it is always best to use the range printed by the laboratory that measured it.

Precision and rounding

Laboratories round results to a sensible number of digits – creatinine in µmol/L is usually reported as a whole number, and in mg/dL to one or two decimal places. Converting a rounded result back and forth can produce small differences: 1.0 mg/dL converts to 88.4 µmol/L, but a reported 88 µmol/L converts back to 0.995 mg/dL. These differences are far smaller than normal biological variation and do not change interpretation.

Worked examples

• Creatinine 1.4 mg/dL: 1.4 × 10,000 ÷ 113.12 = 123.8 µmol/L.
• Creatinine 150 µmol/L: 150 × 113.12 ÷ 10,000 = 1.70 mg/dL.
• Uric acid 420 µmol/L: 420 × 168.11 ÷ 10,000 = 7.06 mg/dL.
• Bilirubin 2.4 mg/dL: 2.4 × 10,000 ÷ 584.66 = 41.0 µmol/L.
• Custom: 5 mg/dL of a substance with molar mass 250 g/mol: 5 × 10,000 ÷ 250 = 200 µmol/L.

Why molar units?

SI units express concentrations by number of molecules rather than weight. That is chemically more meaningful: molecules react with each other one-to-one (or in fixed ratios), not gram-for-gram. Molar units also make it easy to compare substances – for example, to see how much of a filtered load of a substance is reabsorbed. Most of the world adopted SI units for clinical chemistry in the 1970s and 1980s; the United States largely kept conventional units, which is why conversion tools remain so useful.

Other common SI conversions (mmol/L and µmol/L)

Not every test converts to µmol/L – substances present at higher concentrations are reported in mmol/L. The same principle applies (divide by molar mass, adjust for the decilitre), only the final unit is 1,000 times larger.

For glucose, cholesterol and electrolytes, use the dedicated converters: blood sugar mg/dL to mmol/L, cholesterol converter, calcium and magnesium. For electrolyte amounts in medicines, see mEq to mg.

BUN vs urea

The US reports blood urea nitrogen (BUN) – only the nitrogen part of urea – in mg/dL, while the UK, Europe and Australia report urea in mmol/L. Because each urea molecule contains two nitrogen atoms (2 × 14.007 = 28.014 g/mol), BUN in mg/dL × 0.357 gives urea in mmol/L. A BUN of 7–18 mg/dL corresponds to roughly 2.5–6.4 mmol/L urea. This matters for the BUN/creatinine ratio: the SI version (urea mmol/L ÷ creatinine µmol/L) is a different number from the US ratio and has different cut-offs.

Using converted values in calculators

Many clinical formulas were developed with one unit system and silently assume it. If you are entering a result into a calculator or a spreadsheet:

• Check which unit the formula expects. The CKD-EPI eGFR equation uses creatinine in mg/dL; the eGFR calculator accepts both and converts for you.
• Convert before, not after. Converting the output of a formula (such as an eGFR) is meaningless – it is already in its own unit (mL/min/1.73 m²).
• Don't mix units within one formula. A creatinine clearance calculation with urine creatinine in mg/dL and serum creatinine in µmol/L will be wrong by a factor of 88.4 unless both are converted.
• Keep the laboratory's rounding. Over-precise conversions (e.g. 123.76 µmol/L) suggest accuracy that the original measurement does not have.

Which countries use which units?

If you have moved between countries, or you are reading research from another region, expect to see both systems. Many international guidelines publish thresholds in both units for this reason – for example, the KDIGO acute kidney injury criterion of a creatinine rise of 0.3 mg/dL is also given as 26.5 µmol/L.

The three concentration scales at a glance

Hormones and vitamins have their own conversions – for example vitamin D (ng/mL to nmol/L), testosterone (ng/dL to nmol/L) and vitamin B12 (pg/mL to pmol/L). The lab unit converter covers these.

Why creatinine is reported in µmol/L rather than mmol/L

Creatinine concentrations in blood are small – around 0.06–0.11 mmol/L in healthy adults. Writing them as 60–110 µmol/L avoids long strings of decimals and reduces transcription errors. The same reasoning applies to bilirubin and uric acid. Glucose and cholesterol, which are present at much higher molar concentrations, are conveniently expressed in mmol/L.

Common mistakes