Understanding HbA1c and your diabetes blood tests: what every number means

Diabetes and pre-diabetes are diagnosed and monitored through blood tests that measure glucose — the sugar that cells use for energy — and related markers. The most important of these tests is HbA1c, but it is often misunderstood. This guide explains what each test measures, what the numbers mean, and how they fit together.

According to the International Diabetes Federation's 2021 Atlas, over 537 million adults worldwide are living with diabetes — and an estimated 240 million more are undiagnosed. Understanding your blood tests is the first step to acting on them.

HbA1c: the three-month average

HbA1c (glycated haemoglobin, sometimes written as A1C) measures the percentage of haemoglobin — the protein in red blood cells that carries oxygen — that has glucose molecules attached to it. Because red blood cells live for around 90 days, HbA1c reflects your average blood glucose over approximately the past three months. A single high-sugar day won't move it; a persistently elevated glucose over weeks will.

Results are reported as either a percentage (the NGSP system used in the US) or in mmol/mol (the IFCC system used in most other countries). The interpretations:

• **Below 5.7% (39 mmol/mol)** — normal
• **5.7–6.4% (39–46 mmol/mol)** — pre-diabetes (impaired glucose regulation)
• **6.5% (48 mmol/mol) or above** — diabetes (confirmed by a second test on a different day, unless you have clear symptoms)
• **Target for most people already diagnosed with type 2 diabetes:** below 7% (53 mmol/mol)
• **Target for type 1 diabetes:** typically 6.5–7.5% (48–58 mmol/mol), adjusted for individual circumstances

"HbA1c is one of the most powerful numbers in all of medicine. It tells you what your blood sugar has been doing for three months — not just on the day of the test."

Dr. Lina Haddad, CMO, Looms

Why HbA1c isn't the whole picture

HbA1c gives a long-term average but misses short-term variation. Two people can have the same HbA1c but very different day-to-day glucose patterns — one with stable control and one swinging between very high and very low. For this reason, HbA1c is usually interpreted alongside other information.

Certain conditions affect HbA1c accuracy: iron deficiency anaemia, haemolytic anaemia, haemoglobin variants, and chronic kidney disease can all produce misleadingly low or high results. If your doctor suspects a falsely abnormal reading, alternative tests will be used.

Fasting blood glucose

A fasting plasma glucose test measures the glucose in your blood after you have fasted for at least eight hours. It captures your baseline blood sugar without the influence of a recent meal.

• **Below 5.6 mmol/L (100 mg/dL)** — normal
• **5.6–6.9 mmol/L (100–125 mg/dL)** — impaired fasting glucose (pre-diabetes range)
• **7.0 mmol/L (126 mg/dL) or above** — meets the threshold for a diabetes diagnosis (confirmed by repeat testing)

Oral glucose tolerance test (OGTT)

An OGTT involves drinking a standard glucose solution (usually 75 g) and having blood taken two hours later. It tests how effectively your body clears glucose after a sugar load — a more sensitive test for insulin resistance than fasting glucose alone.

• **Below 7.8 mmol/L (140 mg/dL) at two hours** — normal glucose tolerance
• **7.8–11.0 mmol/L (140–199 mg/dL) at two hours** — impaired glucose tolerance (pre-diabetes)
• **11.1 mmol/L (200 mg/dL) or above at two hours** — diabetes

Random plasma glucose

A random glucose test is taken at any time, regardless of when you last ate. It's used primarily when someone has clear symptoms of diabetes — extreme thirst, frequent urination, unexplained weight loss — and a reading of 11.1 mmol/L (200 mg/dL) or above confirms the diagnosis without needing a fasting test.

What brings HbA1c down

For people in the pre-diabetes range or with newly diagnosed type 2 diabetes, lifestyle changes can bring HbA1c back into the normal range — or at least significantly reduce it:

• **Reducing refined carbohydrates and sugars** — white bread, sugary drinks and processed foods cause rapid glucose spikes
• **Increasing fibre** — slows glucose absorption and blunts post-meal spikes
• **Regular physical activity** — exercise increases insulin sensitivity, so the same amount of insulin processes more glucose
• **Weight loss** — even a 5–7% reduction in body weight can halve the risk of progression from pre-diabetes to diabetes
• **Sleep quality** — poor sleep directly increases insulin resistance
• **Medication** — metformin and other agents are often started alongside lifestyle changes, not instead of them

Tracking your results over time

HbA1c is typically checked every three to six months in people with diabetes. The direction of travel — whether it's improving, stable, or worsening — is as important as any individual reading. Looms tracks your lab result trends across tests over time, so you can see your glucose management trajectory clearly rather than relying on memory or scattered paper results.