A Continuous Glucose Monitor (CGM) tracks your blood glucose in real time, giving you access to data that was previously only available through fingerstick tests. This guide helps you interpret your CGM metrics — average glucose, time-in-range, glycemic variability — and understand what they mean for your specific health goal.
Educational use only. This tool provides general educational information about CGM data interpretation. It is not medical advice. Consult your healthcare provider for personalized guidance.
Interpret Your CGM Data
Standard range: 70–180 mg/dL
Below 70 mg/dL (3.9 mmol/L)
Above 180 mg/dL (10.0 mmol/L)
Stability target: CV < 36%
Overall CGM Assessment
Your Personalized Targets
Key Insights for Your Goal
How to Interpret Your CGM Data
CGM devices generate a continuous stream of glucose readings — typically every 5 minutes — that your app summarizes into several key metrics. Understanding what those numbers actually mean can dramatically improve how you use the data to make decisions about food, exercise, and sleep.
Step 1: Enter Your Goal
Different health goals have different target ranges. A person managing Type 2 diabetes has different priorities than an endurance athlete trying to optimize fuel utilization, or someone using a CGM purely for metabolic wellness. Select the goal that best describes your reason for using the device, and this tool will apply the appropriate targets and interpretation context.
Step 2: Enter Your CGM Summary Metrics
Most CGM apps (Dexam Clarity, LibreView, Supersapiens) provide a weekly or 14-day summary. The key metrics are: Average glucose (your mean level over the period), Time in Range (TIR) (% of readings between your target low and high), Time Below Range (TBR) (% below your low threshold), Time Above Range (TAR) (% above your high threshold), and Coefficient of Variation (CV) (how much your glucose fluctuates relative to the mean).
Understanding Time in Range
TIR is considered the most important CGM metric by the American Diabetes Association. For people with diabetes, the standard target range is 70–180 mg/dL and TIR should be above 70%. Each 10% improvement in TIR (roughly 2.4 hours per day) is associated with meaningful reductions in A1C and complication risk. For general wellness, a range of 70–140 mg/dL with TIR above 90% is an excellent target.
Understanding Glycemic Variability (CV)
A Coefficient of Variation below 36% indicates stable glucose control. High variability — big swings from low to high — is harmful even if your average glucose looks acceptable, because the body is repeatedly experiencing glucose spikes followed by reactive lows. Reducing CV typically involves spreading carbohydrates throughout the day, adding protein to meals, and timing carbohydrate intake around exercise.
Unit Conversion
This tool supports both mg/dL (used in the US) and mmol/L (used in most other countries). Toggle the unit switch to convert all reference ranges automatically. The conversion factor is 18.016 — divide mg/dL by 18.016 to get mmol/L.
FAQ
Is this CGM guide free to use?
Yes, this CGM data interpretation guide is completely free. There are no limits, no signup required, and all processing happens locally in your browser. Your health data is never sent to a server.
Is this tool medical advice?
No. This tool provides general educational information about CGM data interpretation. It is not medical advice and should not replace consultation with your healthcare provider. Always discuss your glucose data with your doctor or certified diabetes care educator.
What is Time in Range (TIR)?
Time in Range (TIR) is the percentage of time your glucose stays within a target range (typically 70-180 mg/dL for people with diabetes). The American Diabetes Association recommends TIR above 70% as a key CGM quality metric. Higher TIR is associated with fewer complications.
What is Coefficient of Variation (CV) and why does it matter?
Coefficient of Variation measures glucose variability — how much your glucose swings up and down. A CV below 36% is considered stable. High variability (CV >36%) is associated with increased hypoglycemia risk and worse outcomes, even if your average glucose looks normal.
What glucose range is ideal for athletic performance?
Athletes generally perform best with glucose in the 70-120 mg/dL range during steady-state exercise. Values above 140 mg/dL can impair fat oxidation, while values below 70 mg/dL risk hypoglycemia and energy crashes during training.
How do mg/dL and mmol/L relate to each other?
To convert mg/dL to mmol/L, divide by 18.016. For example, 180 mg/dL equals 10.0 mmol/L, and 70 mg/dL equals 3.9 mmol/L. Most CGM devices can be set to display either unit.
What is a good average glucose for general wellness?
For non-diabetic general wellness, an average glucose below 100 mg/dL (5.6 mmol/L) with TIR above 90% in the 70-140 mg/dL range is considered excellent. Post-meal spikes above 140 mg/dL (7.8 mmol/L) are worth minimizing even without a diabetes diagnosis.