Activity on a Sulfonylurea

If you take a sulfonylurea, exercise needs a small amount of planning — because both the tablet and the activity lower your blood glucose, and together they can go further than either alone.

Increased physical activity is a recognised cause of low blood sugar in people on glucose-lowering medication. The effect is not confined to the session either; muscles keep drawing glucose from your blood for hours afterwards while they restock.

What that means practically:

• Check your glucose before activity, particularly when starting something new or going longer than usual.
• If your reading is at the low end of your range, eat something before you begin rather than starting and hoping.
• Carry fast-acting glucose — tablets, sugar or juice, not chocolate or biscuits.
• Check again afterwards, and be aware of the hours that follow, including overnight after evening exercise.
• Ask your doctor whether your dose should change on days you are more active.

The dose question is worth raising specifically, because people with these subtypes are unusually sensitive to sulfonylureas.

After two or three repeats of the same activity you will know roughly what it does to you, and the planning becomes routine.

If you are not on a sulfonylurea or insulin — for instance untreated GCK-MODY — none of this applies and you can exercise without glucose planning.