Continuous glucose in athletes
Published September 30, 2026 · Reviewed by Nurik Health's medical team against peer-reviewed literatureBefore you keep reading
Nurik is not a medical device and does not diagnose or treat any condition. This page explains how glucose is interpreted in a sports performance context in people without diabetes, and is not guidance for managing diabetes, prediabetes, or any other metabolic condition. If you have one of these conditions, consult your doctor or your endocrinology team before making any decision about your glucose, your nutrition, or your training. Do not use this data to adjust insulin or any medication.
What a CGM measures
A continuous glucose monitor (CGM) is a biosensor that measures glucose in the interstitial fluid — the fluid between cells, just beneath the skin — rather than in blood directly. That's why there's a natural lag of 5 to 15 minutes between what the sensor shows and what a capillary blood glucose meter would show at that same instant: glucose takes that long to diffuse from blood into interstitial tissue. The sensor used in Nurik's biosensor ecosystem (Sibionics GS1) is an interstitial CGM, applied here to a person without diabetes to understand their metabolic response to training and nutrition. That lag has a practical consequence in sport: during intervals or a rapid rise in intensity, the number on screen is already out of date, and the trend arrow is worth more than the point value.
Today the glucose sensor is an optional external biosensor, not built into the base band: when you don't have one connected, Nurik shows dashes ("—") instead of inventing a value, exactly as it does with any other metric that has no sensor.
Why glucose matters to an athlete
Glucose is the fastest-available fuel for moderate-to-high intensity exercise. Seeing how your glucose responds to a meal, a training session, or a night of poor sleep gives you information about your metabolic flexibility — how well your body switches between using glucose and using fat as fuel — that heart rate or sleep alone don't show. This isn't about "lower glucose is better": it's about time in range and stability, not about minimizing the number.
What happens to glucose during exercise
During intense exercise it's normal for glucose to rise transiently: the liver releases glucose into the bloodstream (via glycogenolysis, stimulated by catecholamines and glucagon) at a rate faster than the muscle can consume it in that moment, especially in high-intensity efforts or interval-style training. In prolonged, moderate-intensity exercise, by contrast, glucose can stay stable or even drop as glycogen stores are depleted. Neither pattern is, by itself, cause for alarm in a person without diabetes: it's the normal physiology of effort.
Time in range
Time in range (TIR) is the percentage of the day your glucose stays within a reference range. This is where the most care is needed when reading any glucose data from a healthy athlete, because the appropriate range is not the same as the one used in clinical diabetes management:
| Population | Range used | Source |
|---|---|---|
| People without diabetes (what Nurik uses) | 70–140 mg/dL | Shah et al. 2019, JCEM — CGM in healthy adults |
| Clinical diabetes management | 70–180 mg/dL | Battelino et al. 2019, international consensus on CGM clinical targets |
Shah 2019 describes the observed glucose behavior in adults without diabetes; it doesn't propose a therapeutic target. Nurik uses it as a descriptive reference.
The 70–180 mg/dL range is a clinical management target, not a description of what's normal in someone without diabetes: using it here would leave time in range at nearly 100% almost always and wouldn't convey any information. That's why Nurik uses the descriptive range for a healthy population. This doesn't imply that an excursion between 140 and 180 is abnormal.
Glycemic variability
Beyond the average or time in range, how stable glucose stays matters on its own. Nurik measures this with the coefficient of variation (CV%), calculated as the standard deviation of the readings divided by the mean, multiplied by 100.
WEAK / EXTRAPOLATED EVIDENCE
Nurik currently uses a CV% < 36% threshold, taken from the international consensus on CGM interpretation, where it was defined for a population with diabetes. In people without diabetes, typical CV is quite a bit lower (on the order of 15–20%), so this threshold is a borrowed reference, not a cutoff validated in healthy athletes.
A high CV% is not automatically a health problem in a person without diabetes — it can simply reflect a heavy dinner or a late training session on a given night — but sustained over time it's a signal of glycemic variability worth observing together with sleep and nutrition, never interpreted in isolation or as a diagnosis.
The low-glucose alert
Nurik flags an alert when nighttime minimum glucose falls below 55 mg/dL, a clinically recognized hypoglycemia threshold. In a person without diabetes this is uncommon outside very prolonged fasting or extreme effort without carbohydrate replacement, and the alert exists so that data point doesn't go unnoticed — not to suggest a diagnosis or a treatment. If an alert like this occurs, especially if it repeats, the right step is to consult a doctor.
A very common cause of a low nighttime reading is pressure on the sensor from your body while you sleep ("compression lows"), not a real hypoglycemia. An interstitial CGM doesn't confirm hypoglycemia: that's confirmed with capillary blood.
Frequently asked questions
Is this page guidance for managing diabetes?
No. Nurik is not a medical device and does not diagnose or treat any condition. This page does not replace a doctor's instructions. If you have diabetes, prediabetes, or any metabolic condition, the management of your glucose must be guided by your healthcare team.
Is it normal for glucose to rise during exercise?
Yes, in a person without diabetes. The liver releases glucose faster than the muscle consumes it in intense efforts. It's a normal physiological response, not a warning sign by itself.
What is time in range?
The percentage of time your glucose stays within a reference range. In people without diabetes, Nurik uses 70–140 mg/dL; the 70–180 mg/dL range is used by clinical consensus guidelines for diabetes management, and it's not interchangeable with the former.
References
Shah, V.N. et al. (2019). "Continuous Glucose Monitoring Profiles in Healthy Nondiabetic Participants: A Multicenter Prospective Study." The Journal of Clinical Endocrinology & Metabolism.
Battelino, T. et al. (2019). "Clinical Targets for Continuous Glucose Monitoring Data Interpretation: Recommendations From the International Consensus on Time in Range." Diabetes Care.
Thresholds and criteria taken from Nurik's app code, validated by its medical team, and from the references cited above. No thresholds or figures are included that weren't backed by that source.
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