What A1C measures
Sugar (glucose) in your blood sticks to hemoglobin, the protein inside red blood cells. The A1C test measures what share of your hemoglobin has glucose attached. Red blood cells live for about three months, so the result reflects your average glucose over roughly the past two to three months, with the most recent weeks counting a bit more.
The result is a percentage. A large study translated A1C into an "estimated average glucose" in the same units as a meter. For example, an A1C of 7% matches an average glucose of about 154 mg/dL, and each 1% step up adds roughly 28–29 mg/dL.4
What A1C goal is right for me?
For many adults with diabetes who are not pregnant, the American Diabetes Association (ADA) suggests an A1C goal below 7%, as long as it can be reached safely, without frequent or severe low blood sugar.1 That is a starting point, not a rule for everyone:
- A lower goal may make sense for some people if it can be reached safely with few lows.
- A less strict goal is often better for people with frequent lows, a history of severe hypoglycemia, other serious health problems, or limited life expectancy.
- Pregnancy uses different, tighter targets, set with your obstetric care team.
Your goal should be agreed between you and your clinician, and it can change over time as your health and treatment change.
Where A1C falls short
A1C is an average, and averages hide detail. Two people can share an A1C of 7%: one with steady readings, the other swinging between highs and lows. The second person may feel worse and face more risk from low blood sugar, yet the A1C looks the same.
A1C can also be misleading when red blood cells are not "average." Conditions that change how long red cells live, such as some types of anemia, recent blood loss or transfusion, certain hemoglobin variants, advanced kidney disease and pregnancy, can push the number up or down without a true change in glucose.2 If your A1C and your meter or CGM readings don't seem to agree, mention it. That mismatch is useful information.
What "time in range" means
A continuous glucose monitor (CGM) checks glucose every few minutes, all day and night. From those readings, your CGM report can show what percentage of the time your glucose stayed in a target range. For most people with type 1 or type 2 diabetes, that range is 70 to 180 mg/dL.3
An international consensus panel set out goals that the ADA Standards of Care now use for many non-pregnant adults:31
| Measure | Goal | Roughly per day |
|---|---|---|
| Time in range (70–180 mg/dL) | More than 70% | Over 16 hours 48 minutes |
| Time below 70 mg/dL | Less than 4% | Under 1 hour |
| Time below 54 mg/dL | Less than 1% | Under 15 minutes |
| Time above 180 mg/dL | Less than 25% | Under 6 hours |
| Time above 250 mg/dL | Less than 5% | Under 1 hour 12 minutes |
For older adults or people at higher risk of low blood sugar, the consensus suggests gentler goals: more than 50% time in range and less than 1% of time below 70 mg/dL.3 The ADA also notes that if time below range is above goal, treatment should usually be adjusted.1
How the two numbers fit together
About 70% time in range lines up, on average, with an A1C near 7%.3 But each number answers a different question:
- A1C: "What has my average been over the past few months?"
- Time in range: "How much of my day was spent where I want to be, and when do I go high or low?"
Your CGM report may also show a glucose management indicator (GMI). This is an estimate of what your A1C would be based on CGM data alone. GMI and lab A1C often differ a little. Neither one is "wrong"; the gap is something to discuss with your clinician.
For a CGM report to be reliable, the consensus recommends at least 14 days of data with the sensor worn about 70% of the time or more.3
Making the numbers useful
Numbers are only helpful if they lead to a plan. A few tips that many people find practical:
- Look for patterns, not single readings. One high after a birthday dinner matters less than a high that shows up every afternoon.
- Look at lows first. Preventing low blood sugar is usually the first priority, because lows can be dangerous right away.
- Bring your data to visits. If you use a CGM, share or bring your report. If you use a meter, bring the meter or a log.
- Small changes add up. Moving from 60% to 65% time in range is about an extra hour in range each day.
When to call your care team
Contact your clinician if you are having frequent lows, lows you don't feel coming, readings that stay well above your target, or numbers that don't match how you feel. If you have a severe low and cannot treat it yourself, or you feel very unwell with high readings, vomiting or trouble breathing, call 911.
This article is general education. Your own goals depend on your health, medicines and preferences, and should be set with your care team.
Sources & references
- American Diabetes Association Professional Practice Committee for Diabetes. 6. Glycemic Goals, Hypoglycemia, and Hyperglycemic Crises: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S132–S149. doi:10.2337/dc26-S006. View source
- American Diabetes Association Professional Practice Committee for Diabetes. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1). doi:10.2337/dc26-S002. View source
- Battelino T, Danne T, Bergenstal RM, et al. Clinical targets for continuous glucose monitoring data interpretation: recommendations from the International Consensus on Time in Range. Diabetes Care. 2019;42(8):1593–1603. doi:10.2337/dci19-0028. View source
- Nathan DM, Kuenen J, Borg R, et al. Translating the A1C assay into estimated average glucose values. Diabetes Care. 2008;31(8):1473–1478. doi:10.2337/dc08-0545. View source
Guidelines are updated over time. Links point to the publisher or DOI record; always check for the newest version.