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How to tell if you or someone you know is underweight

This is one guide that can help you discover whether someone is underweight. Other signs are listed on information for older people. And don’t forget to speak to your practice nurse or GP.


To measure mid upper-arm circumference – a way of telling if someone is underweight, you can use any tape measure. Or you may have had a measure and guide in your Derbyshire Gold magazine. Watch the video about how to use it.

Or follow these instructions:

  1. First find the middle point of your upper arm. You’ll probably need help when you do this. Ask a relative, carer or friend.
  2. Bend your left arm at the elbow so that it’s at a right angle (90 degrees).
  3. Measure the distance between the top of your shoulder and the point of your elbow, down the left outside of your arm.
  4. Mark the mid-point with washable ink. For example, if your measurement is 32cm, the mid-point is 16cm.
  5. Then measure your mid-upper arm circumference (abbreviated to MUAC) and hang your arm loose.
  6. Measure around the upper arm at the mid-point you have just marked. The tape should touch your skin all the way around but not be pulled too tightly.
  7. If your MUAC measurement is 23.5cm or less then you should seek further advice.
  8. Ask your doctor or your practice nurse if you need to address your weight. You may be underweight and need to boost your food intake.
  9. If your MUAC is more than 32cm, you may need help to lose weight.