What is Managing Type 1 Diabetes During Exercise?

How to prevent hypos, adjust insulin and carbs, and safely train with type 1 diabetes.

Diabetes

Managing Type 1 Diabetes During Exercise

2025-08-30 • Updated 2025-09-13

Intro

Exercise is one of the best tools for improving glucose control, cardiovascular health, mood, and sleep.
With type 1 diabetes (T1D), the main challenge is avoiding hypoglycaemia during and after activity while still gaining the benefits.
With planning and monitoring, most people with T1D can safely enjoy any sport.

Key Points

Aerobic activity (steady cardio) usually lowers glucose during and after.
Anaerobic/high-intensity or strength may cause a temporary rise, sometimes followed by a later drop.
Always check glucose before exercise and keep fast carbs within reach.
Use CGM trend arrows to act early.
Watch for late-onset hypos (up to 24h after prolonged or evening sessions).

Pre-Exercise Checklist

✅ Check glucose (and CGM trend if available).
✅ Carry 15–30 g fast carbs (glucose tabs/gel/juice).
✅ Hydrate well.
✅ Wear medical ID indicating T1D.
✅ Don’t exercise alone if prone to severe hypos.
✅ Check infusion sites/sensors — avoid pressure or direct hits.

Quick Decision Table — Starting Glucose

Starting glucose	Action
<5.6 mmol/L (<100 mg/dL)	Take 15–20 g fast carbs, recheck in 15 min. Delay exercise until ≥5.6.
5.6–10 mmol/L (100–180 mg/dL)	Safe range. For aerobic: reduce pre-meal bolus (–25–50%) or temp basal (–20–50%). Take 10–20 g carbs at start if needed.
>10–13.9 mmol/L (180–250 mg/dL)	Usually safe to start. Monitor closely; correction may not be needed before exercise.
>13.9 mmol/L (>250 mg/dL)	Check ketones. If positive → do not exercise; give correction and hydrate. If negative → light activity only until trending down.

During Exercise

Recheck every 30 minutes (or track CGM).
Take 10–20 g carbs if dropping or if symptoms suggest a low.
Mix fast carbs (for quick rescue) with slower carbs (banana, bar) for long sessions.
⚠️ Remember: hypo symptoms can mimic normal exercise fatigue → check, don’t guess.

After Exercise (and Overnight)

Risk of delayed hypos is highest after:
- Long aerobic sessions
- Evening workouts
- Unfamiliar/new activities
Consider:
- Temp basal reduction (pump: –10% to –30% for 6–12h).
- Bedtime snack with carb + protein if trending low.
- Raising CGM low alerts overnight on training days.
Monitor more closely for up to 24 hours after prolonged sessions.

Site Management

Rotate infusion and sensor sites.
Avoid sites that take direct impact or heavy friction.
For swimmers/sweaty sports: use overpatches/extra adhesive.
Plan site changes before competitions, not during.

Sick Days & Heat

Illness and heat can raise glucose and increase insulin needs.
Monitor more often; adjust with clinical guidance.

Red Flags — Seek Medical Advice

Repeated severe hypos needing assistance.
Ketones that don’t resolve with correction and fluids.
Unexplained persistent highs during/after light activity.
⚠️ Any loss of consciousness during activity → review safety plan with your team before resuming.

FAQ

Do I need different targets for competition days?
Yes, some athletes run slightly higher targets to reduce hypo risk — discuss with your team.

Are sports drinks okay?
Yes, during long or high-intensity sessions. Otherwise, stick to water and planned carbs.

Pump vs. injections for sport?
Pumps allow temp basal adjustments. With MDI, pre-planning bolus reductions and timed carbs also works well.