Two measurements come up again and again in diabetes care: blood glucose and HbA1c. They answer different questions, and understanding the difference makes appointments easier to follow.
Blood glucose: a snapshot
Blood glucose is the amount of glucose in your blood at a particular moment. It rises after meals and falls with activity, illness, stress, sleep and medicines. It can be checked with a finger-prick meter, with a laboratory test, or with a continuous glucose monitor (CGM), which reads glucose every few minutes through a small sensor.
HbA1c: the longer view
HbA1c (often called A1C) reflects your average blood glucose over roughly the past two to three months. It works because glucose attaches to haemoglobin, a protein in red blood cells, and red blood cells live for about three months. HbA1c is reported either as a percentage (for example 7%) or in mmol/mol. A higher HbA1c means glucose has been higher on average.
Health authorities commonly use an HbA1c of 6.5% (48 mmol/mol) or above as one of the criteria for diagnosing diabetes, but a diagnosis depends on the full clinical picture and usually on repeat testing.
Your target is personal
There is no single perfect number for everyone. Targets depend on age, type of diabetes, other health conditions, risk of low blood glucose, pregnancy and personal circumstances. Always ask your healthcare team what range is right for you and how often to test.
Things that can affect an HbA1c result
Some situations can make HbA1c less reliable, including anaemia, some inherited haemoglobin variants, recent blood loss or transfusion, pregnancy and kidney disease. If your HbA1c does not match your daily readings, ask whether another test might help.
Making sense of the numbers
- Look for patterns over days and weeks rather than reacting to one reading.
- Note what was happening around unexpected highs or lows: meals, activity, illness, medicines, stress.
- Bring your readings, meter or sensor data to appointments.
- Ask what “time in range” means if you use a CGM.
Do not change medicines or treatment because of a number you have read online. Discuss changes with your healthcare team.
Evidence & Research
- Author
- pktqu
- Published
- October 15, 2026
- Last reviewed
- September 25, 2026
References
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The A1C test and diabetes. https://www.niddk.nih.gov/health-information/diagnostic-tests/a1c-test-diabetes
- World Health Organization. Diabetes fact sheet. https://www.who.int/news-room/fact-sheets/detail/diabetes
- International Diabetes Federation. About diabetes. https://idf.org/about-diabetes/
Important: This information is for general education and does not replace personalised medical advice, diagnosis or treatment. Speak with an appropriate qualified healthcare professional about your health.