Continuous Glucose Monitors for Triathletes: Worth It in 2026?

Continuous glucose monitors (CGMs) — the small skin-mounted sensors originally built for people with diabetes — have started turning up on non-diabetic endurance athletes over the past few years. They promise real-time insight into how your body handles fuel during training. Here’s what the evidence actually says before you spend money on one.

What a CGM Actually Measures

A CGM sensor sits just under the skin and measures glucose in interstitial fluid — the fluid between cells — rather than blood directly. It’s a proxy for blood glucose, with a short lag, updated every few minutes and viewable on a phone app throughout the day and during sessions.

Where the Evidence Is Genuinely Useful

• Fuelling strategy — seeing how your glucose behaves across a long ride can highlight whether you’re under-fuelling early and bonking late, a pattern many age-groupers only discover mid-race.
• Exercise-associated hypoglycaemia — some athletes see genuine low-glucose dips during or after very long sessions; a CGM can flag this pattern for you and a coach or dietitian to act on.
• Sleep and recovery context — overnight glucose stability is sometimes used as one more data point alongside HRV and resting heart rate, though it shouldn’t be treated as a standalone recovery score.

Where to Be Sceptical

Sports science research on CGM use in non-diabetic endurance athletes is still young. There’s no agreed set of “normal” reference ranges for athletes during hard exercise the way there is for resting adults, and elite endurance athletes often show large glucose swings during competition that would look alarming in a clinical context but may simply reflect normal exercise physiology. In plain terms: the data is real, but interpreting it correctly without a sports dietitian is genuinely difficult, and chasing a “flat line” isn’t necessarily the goal.

Should You Get One?

If you’re an age-grouper training for a sprint or Olympic race, a CGM is unlikely to tell you anything a well-practised fuelling routine and a basic nutrition log won’t. Where it earns its cost is long-course training — 70.3 and full-distance athletes wrestling with race-day fuelling, or anyone with a specific, recurring bonk pattern they can’t otherwise diagnose. Even then, the sensor is only half the value — pair it with a sports dietitian who can actually interpret the trace, rather than reading raw numbers in isolation.