What is HbA1c and what is a healthy level?

What is hemoglobin HbA1c and what does the lab test measure?

In the lab, a blood sample is checked for the share of your hemoglobin that carries glucose. The more glucose in your blood, the more attaches, so the result reflects a pattern over time rather than what you ate this morning.

The number can also be nudged by things unrelated to sugar. Iron deficiency can make A1C read falsely high, and hemoglobin variants, more common in people of African, Mediterranean or Southeast Asian descent, can make it unreliable. If either applies to you, it is worth mentioning when the test is ordered, so your primary care provider (GP in the UK) can read the result with that in mind.

HbA1c is one of the tests used to look for raised blood sugar, alongside a fasting plasma glucose test and an oral glucose tolerance test (OGTT).

What does the evidence say about HbA1c in women?

The evidence shows that HbA1c matters most for women at a few particular points: after gestational diabetes, with PCOS, and from midlife onward. PCOS and gestational diabetes both raise the chance of developing diabetes later, a link the International PCOS Guideline (2023) sets out, so either one is worth mentioning whenever blood sugar comes up.

Insulin resistance rises in midlife, and type 2 diabetes risk keeps rising with age after menopause, which is why the check becomes a regular one from perimenopause. Two companion checks are often read beside it: a waist to height ratio, and cholesterol, since SWAN (the Study of Women's Health Across the Nation) tracks LDL cholesterol rising over the same years. Our guide to high cholesterol symptoms in women covers that one, and our guide to high fiber foods gives the daily amounts for the food side of blood sugar.

A single result is not a diagnosis. NIDDK notes that a diagnosis needs a second confirming measurement unless clear symptoms are present, so one reading in the prediabetes or diabetes band is the start of a conversation rather than the end of one.

A result above the healthy range is also common. In the US, 115.2 million adults have prediabetes, according to the CDC, which is the plain case for a routine check now and then, since it can show a change before anything feels different. It is one reading among several, most useful when looked at gently and regularly.

How often should women check HbA1c?

Every 1–3 years is the rhythm the Women's Preventive Services Initiative Well-Woman Chart supports. In the reproductive years that applies after gestational diabetes, and otherwise when risk is higher. From perimenopause onward it applies more generally.

In the US, the USPSTF (2021) recommends screening for prediabetes and type 2 diabetes in adults aged 35 to 70 without symptoms, using HbA1c or either of the other blood sugar tests (Grade B). The entry criterion is worded around body weight. That is a rule for who is offered a test, not a goal, and a history of gestational diabetes or PCOS is reason enough to ask about a check whatever your size.

In the UK, Diabetes UK describes 48 mmol/mol (6.5%) or below as an ideal HbA1c for people living with diabetes. That is a treatment target for someone already diagnosed, which is a different job from a routine check.

What did the studies show, and what did they not show?

The strongest trial evidence comes from the Diabetes Prevention Program, a large US study of adults at high risk of type 2 diabetes. Lifestyle change cut the risk of developing type 2 diabetes by 58% over about 3 years compared with placebo, and metformin cut it by 31%. At 15 years of follow-up the delay in onset was still 27% for lifestyle and 18% for metformin.

What the trial did not show is just as useful to know. It measured who went on to develop type 2 diabetes, so it gives no figure for how far HbA1c falls with any one habit. The CDC's national counts are also not split by sex, so they describe US adults as a whole rather than women specifically.

Next steps

A good place to start is your most recent result: if you have one, note the date and the number beside the ranges at the top of this page. If you have never had the test, or it was a while ago, you might ask your primary care provider (GP in the UK) whether a check makes sense for your history and stage of life. From there, movement, food and when to retest are options rather than assignments, so you can pick what suits your days, or nothing for now. The choice is yours, and what fits one woman's life may not fit another's: this is not one size fits all.