🩺 Diabetes Tech
Continuous Glucose Monitors (CGM) — Complete Guide for 2026
Everything about CGMs — how they work, best devices (Libre, Dexcom), who should use them, and whether non-diabetics benefit. Updated January 2026.
Key Takeaways
- CGMs measure glucose every 1–5 minutes — providing far more data than finger-prick testing
- The FreeStyle Libre 3 and Dexcom G7 are the leading devices in UK and USA
- NHS provides CGMs free to all Type 1 diabetics and some high-risk Type 2 patients
- Non-diabetics using CGMs (biohackers) gain valuable personalised food response data
- CGMs have reduced HbA1c in Type 1 by an average of 0.3–0.4% in clinical trials
How CGMs Work
A Continuous Glucose Monitor (CGM) consists of a tiny sensor filament inserted just under the skin (typically arm or abdomen) that measures glucose in the interstitial fluid every 1–5 minutes. This data is transmitted wirelessly to a smartphone app or receiver, providing real-time glucose readings, trends, and alerts.
Every 1 min
FreeStyle Libre 3 reading frequency
0.3–0.4%
Average HbA1c reduction from CGM use in Type 1 diabetes
14 days
Wear duration for FreeStyle Libre 3 sensor
Leading CGM Devices 2026
| Device | Reading Interval | Sensor Duration | NHS Available | Price (UK private) |
|---|---|---|---|---|
| FreeStyle Libre 3 | Every 1 minute | 14 days | Yes (T1D, T2D insulin) | ~£50/month |
| Dexcom G7 | Every 5 minutes | 10 days | Yes (T1D) | ~£80–90/month |
| Dexcom ONE+ | Every 5 minutes | 10 days | Yes (T1D, T2D insulin) | ~£60/month |
| Medtronic Guardian 4 | Every 5 minutes | 7 days | T1D pump users | Via pump systems |
| Stelo (OTC, USA) | Every 15 minutes | 15 days | USA only | ~$99/month |
Who Should Use a CGM?
Medical Indications (Strong Evidence)
- Type 1 diabetes: NHS now provides CGM free to all — dramatically improves HbA1c and reduces hypoglycaemia
- Type 2 on insulin: Reduces HbA1c, reduces hypoglycaemia incidents
- Gestational diabetes: NICE recommends CGM during pregnancy for better outcomes
- Type 2 not on insulin: Growing evidence for improved self-management and HbA1c
Non-Diabetic Use (Emerging)
A growing 'biohacker' and wellness market uses CGMs to understand personal glucose responses to foods, exercise, and lifestyle. Products like the Stelo (USA, OTC) and Libre Sense (now discontinued) were developed for this market. Evidence for specific health benefits in non-diabetics is still limited but the personalised data can be motivating for dietary changes.
✅ How to Get a CGM on the NHS
Type 1 diabetes: ask your diabetes team — all T1D patients are now entitled to CGM on NHS. Type 2 on insulin: discuss with your GP or diabetes nurse. Type 2 not on insulin: may be available via your diabetes team if clinical criteria are met. If not eligible for NHS: FreeStyle Libre 2 or 3 sensors are available from pharmacies and online for approximately £50/month.🔢 Free Tool
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Is FreeStyle Libre or Dexcom better?▼
Libre 3 has the most frequent readings (every minute), longest NHS availability, and lowest cost. Dexcom G7 has slightly better accuracy (MARD 8.2% vs 9.2%), better integration with insulin pumps (closed-loop systems), and real-time sharing capabilities — important for parents of T1D children or those using pump therapy. For most people on the NHS, whichever is prescribed is appropriate.
Can non-diabetics use a CGM?▼
Yes — no prescription is required for most CGM sensors. In the USA, Stelo is specifically FDA-approved for non-diabetic use. In the UK, FreeStyle Libre sensors can be purchased over the counter from pharmacies. The main value for non-diabetics is understanding personal glucose responses to specific foods, stress, sleep, and exercise.
How accurate are CGMs?▼
Modern CGMs are highly accurate for trend monitoring and treatment decisions. Mean Absolute Relative Difference (MARD): Dexcom G7: 8.2%, FreeStyle Libre 3: 9.2%. This means readings may be within ~8–9% of the true blood glucose value. CGMs measure interstitial fluid glucose — which lags behind blood glucose by 5–15 minutes, important during rapid glucose changes.
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⚕️ Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting or changing any medication or treatment.
Dr
Dr. Priya Sharma, MD
WellCalc Medical Contributor
All articles reviewed by qualified healthcare professionals following NHS, AHA, and WHO guidelines.