Working muscle absorbs glucose from the blood through a pathway that does not require insulin at all. That is why a walk lowers glucose, and why the effect keeps going after you stop — muscles refill their glycogen stores for up to 24 hours afterwards, and insulin sensitivity stays improved for roughly that long.
The target
150 minutes of moderate activity a week, spread over at least three days, with no more than two consecutive days off. Add resistance work — weights, bands, bodyweight — twice a week; muscle mass improves insulin sensitivity in a way cardio alone does not. "Moderate" means you can talk but not sing.
If that sounds unreachable, start with ten minutes after your largest meal. The post-meal walk has an outsized effect on the daily glucose curve relative to how easy it is to do.
Why some exercise raises glucose
Not all activity lowers glucose in the moment. Short, intense effort — sprinting, heavy lifting, a competitive match — triggers adrenaline and cortisol, which tell the liver to release stored glucose faster than the muscles use it. You can finish a hard session with a higher reading than you started. This is normal, usually settles within an hour or two, and is not a reason to avoid intense exercise. It is a reason not to correct it aggressively.
If you use insulin
- Test before you start. Below 100 mg/dL (5.6 mmol/L), eat 15–30 g of carbohydrate first. Above 250 mg/dL (13.9 mmol/L) with ketones, postpone.
- Exercising within two to three hours of a rapid insulin dose carries the highest risk of a low, because insulin action and muscle uptake add together.
- Test again afterwards, and again before bed. Post-exercise lows classically arrive six to twelve hours later, overnight.
- Carry fast-acting carbohydrate. Always.
- Avoid injecting into a limb you are about to work hard — absorption speeds up.
- Ask your doctor about reducing the pre-exercise dose. For planned activity this is often a better tool than eating extra.
When to be careful
Some complications change what is safe. Advanced retinopathy makes heavy straining and high-impact activity risky. Significant neuropathy in the feet means checking them before and after, and choosing low-impact options with proper footwear. Uncontrolled high blood pressure or known heart disease should be discussed before starting anything vigorous. None of these rule out exercise — they change which exercise.
Log your activity alongside your readings. The relationship between a session and the glucose that follows it is highly individual, and after a few weeks of records yours becomes predictable enough to plan around.