How to Read a Blood Glucose Mmol/L Scale

Written by dr. bob goat
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Blood glucose is normally maintained between a narrow range of concentrations. These concentrations are presented as either mass per volume (milligrams per decilitre) or as moles per volume (millimoles per litre). It is important to understand how to convert between the two readings and what normal ranges are in each scale. This article will show conversions between the two concentration presentations, to demonstrate how to read a blood glucose in the mmol/L scale.

Skill level:

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Things you need

  • glucose meter (available at the chemist)
  • calculator

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  1. 1

    Obtain a blood glucose reading with a glucose meter (glucometer).

  2. 2

    Determine the scale that the meter is using for measurements.

  3. 3

    Compare the results to the reference ranges.

    The American Diabetes Association indicates fasting plasma glucose (pre-meal) should be between 90 to 130 mg/dl (5 to 7.2 mmol/l) and glucose tolerance levels (post-meal) >180 mg/dl (10 mmol/l).

  4. 4

    Convert the numbers:

    To convert blood glucose from mg/dl to mmol/L, divide by 18. To convert blood glucose from mmol/L to mg/dl, multiply by 18.

    Conversions are based on a molecular weight of glucose of 180 grams per mole, divided by 10 to move from litre to decilitres, which yields 18 as the conversion factor between the concentrations.

Tips and warnings

  • Make sure to use the correct scale, reporting mg/dl for a mmol/L will appear dangerously high (hyperglycaemia), and using mmol/L on a mg/dl will appear extremely low (hypoglycaemia).
  • Use the glucometer with caution, probes will be sharp.
  • If blood glucose falls outside the normal range, seek medical attention.

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