Units
Hemoglobin units: g/dL, g/L and mmol/L
Hemoglobin (haemoglobin) is reported in g/dL in some countries, g/L in others and mmol/L in a few. Here is how they relate, with a worked conversion.
By FerroLady · Updated · 4 min read
Hemoglobin, spelt haemoglobin in the UK and Australia, is reported in grams per decilitre (g/dL) in the United States and in grams per litre (g/L) in many other countries. A few, including the Netherlands and Denmark, use millimoles per litre (mmol/L). The three are different ways of writing the same measurement.
g/dL and g/L differ by a factor of ten
There are ten decilitres in a litre, so one gram per decilitre is ten grams per litre:
- g/dL × 10 = g/L
- g/L ÷ 10 = g/dL
A value written as 12.0 g/dL is the same quantity as 120 g/L. The digits are very different, which is why the unit has to travel with the number.
Converting to mmol/L
To convert grams per litre to millimoles per litre, divide by 16.114, which counts hemoglobin per haem group. From g/dL, divide by 1.6114:
- g/L ÷ 16.114 = mmol/L
- g/dL ÷ 1.6114 = mmol/L
- mmol/L × 16.114 = g/L
So 12.0 g/dL is 120 g/L, which is 7.4 mmol/L to one decimal place.
A common mix-up
The numbers 12 and 120 can describe the same sample, and 12 and 12 in different units cannot. If you keep results from more than one country, or more than one laboratory, record the unit each time and check it against the printed report rather than relying on how large the number looks.
How FerroLady handles units
FerroLady keeps each result in the unit you entered, never rewrites what you saved, and always shows the unit beside the value.
