Statistically, men are more likely than women to be diagnosed with type 2 diabetes, with about 18 million more men living with the condition worldwide. This doesn’t tell the whole story. When women do get a diagnosis, they’re often older and have a higher body fat mass. They’re also more likely to die from diabetes-related causes, especially heart disease. And some researchers think underdiagnosis might explain part of the gap—perhaps more cases are being missed in women.

To address this disparity, researchers are trying to understand more about the biological and social differences that contribute to later diagnoses and worse outcomes in women, with some suggesting it’s time health care providers change the way they test for diabetes in order to catch at-risk women earlier, when treatments and lifestyle changes can have more impact.

There are several potential reasons behind the differences in diagnosis for men and women. While many risk factors for type 2 diabetes are universal, they tend to show up later in women. The disease may also present differently in women, which could lead current diagnostic tools to overlook them. Using some tests but not others is a “major reason for underdiagnosis of diabetes in women,” says Michael Leutner, a professor in endocrinology and metabolism and a member of the Gender Medicine Unit at the Medical University of Vienna.

We know there are biological differences between the sexes that affect type 2 diabetes—particularly the impact of hormones. Major hormonal shifts throughout a person’s lifetime can influence how their bodies manage blood sugar, with life events such as pregnancy and menopause affecting how type 2 diabetes develops and progresses.

Gestational diabetes during pregnancy “is one of the most powerful harbingers of things to come,” says Judith Regensteiner, a professor of medicine and director of the Ludeman Family Center for Women’s Health Research at the University of Colorado Anschutz Medical Campus. In fact, a gestational diabetes diagnosis is the single biggest risk factor for type 2 diabetes in women, with some studies suggesting women who experience gestational diabetes are up to eight times more likely to develop type 2 diabetes later in life.

Other hormonal shifts over a woman’s lifetime can influence type 2 diabetes risk and progression. How and where fat is stored in the body, for instance, is a key risk factor for type 2 diabetes in everybody, but not all fat is created equal. At younger ages, men are more likely than women to store visceral fat. “That’s the deep belly fat that sits deep around the organs,” explains Peter Goulden, associate professor at the Icahn School of Medicine and chief of the Division of Endocrinology, Diabetes and Metabolic Bone Disease at Mount Sinai in New York.

Visceral fat is particularly harmful because it releases free fatty acids which increase resistance to insulin—the hormone which regulates blood sugar. Insulin “is the key that unlocks the cells, so the glucose can go into the cells,” Goulden says. With insulin resistance, the body’s cells stop responding to insulin as effectively, and glucose builds up in the blood.

Before menopause, women tend to store fat around the hips and thighs, “which is actually less harmful metabolically,” says Goulden. But the hormonal changes during menopause, especially the decline in estrogen, mean the body stores more visceral fat. This accumulation of deep belly fat is actually worse for women than for men: Each kilogram of visceral fat increases a woman’s risk of developing type 2 diabetes by about seven times—around triple the risk seen in men, according to a 2019 study.

The role of menopause on visceral fat might help explain why women tend to be diagnosed with type 2 diabetes at an older age. This type of fat can also build up without necessarily pushing someone into the obese weight category, so common tools such as body mass index (BMI) can miss early risks. One study found that BMI was more strongly associated with type 2 diabetes in men than women; measurements related to waist size were a stronger predictor for women. Last year, the American Diabetes Association updated its guide on diabetes management to recommend measurements such as waist circumference be taken into account in addition to BMI when assessing obesity.

Menopause may influence diabetes in other ways, too. Estrogen is thought to play a protective role in blood sugar regulation. When the hormone binds to its receptor, it helps cells respond to insulin better and protects pancreatic beta cells—responsible for producing and releasing insulin—from damage. But as estrogen levels drop with the onset of menopause, so does the body’s ability to manage blood sugar as effectively. That drop is believed to be another big reason why the risk of developing type 2 diabetes rises for women during midlife. “I think the message from this is that really there should be lifelong screening,” says Goulden.

While these hormonal factors explain why many women may develop type 2 diabetes later than men, there are also concerns that diagnostic tools might not catch the early signs of the disease in younger women as well as they do in men. A common diagnostic procedure is the hemoglobin A1c (HbA1c) blood test, which is often used because it’s convenient and doesn’t require fasting. The test measures the amount of hemoglobin in the blood that is coated with sugar; this acts as an indicator of average blood glucose levels over a few months, since the lifespan of red blood cells is around three months. But recent evidence suggests it might not pick up diabetes risk in some younger women.

Before menopause, women typically have lower levels of HbA1c than men of the same age. Researchers in Taiwan therefore suggest that “the HbA1c cut-off point for the diagnosis of diabetes should vary by age and gender.” A 2023 study from the UK, which analyzed data from more than a million people, similarly found that women had slightly lower average HbA1c levels than men. The researchers estimated that if the diagnostic threshold was reduced, 35,000 more women in England and Wales could be diagnosed.

But for now, cutoffs remain the same for men and women, and experts say there isn’t yet enough evidence to warrant a change. “I wouldn’t say there’s enough data there to support saying that there should be different cutoffs,” Goulden says.

“We need more prospective clinical studies to investigate it,” says Leutner. He argues that, rather than adjusting HbA1c thresholds, clinicians should make greater use of the oral glucose tolerance test (OGTT), a more sensitive tool for detecting diabetes in its early stages but one that involves fasting before having blood glucose levels measured before and after drinking a sugary drink. Men are more likely to have elevated glucose levels caught during routine blood work, says Leutner. “Females on the other hand more often have impaired glucose tolerance, which can only be measured with the more complex OGTT,” he says.

Catching type 2 diabetes early is essential in reducing some of its greatest associated harms. One aspect is limiting the risk of cardiovascular disease. While men are more likely to develop heart disease in general, type 2 diabetes tips this balance: fatal heart disease associated with diabetes is 50 percent more common in women than men. Even so, says Regensteiner, “heart disease may go undetected for longer in women.”

Social differences can also play a role in the different outcomes between women and men, says Regensteiner. In her experience, some women can be dismissive of the condition. “I’ve heard people say, ‘I’ve got a little bit of diabetes,’ and that’s like being ‘a little bit pregnant,’” she says. “It’s not a little bit. It’s a serious disease.” Clinicians can underestimate the risks too: Women with type 2 diabetes are less likely to be prescribed certain cardioprotective medications than men.

As research continues, it’s important that sex differences are taken into account. Historically, women were left out of many early studies that shaped risk guidelines for diseases, including type 2 diabetes. When they were included, it was often in smaller numbers, and their data wasn’t separated out, Regensteiner says. “That hurts both sexes, because the results are muddied,” she says. “There are sex differences, and ignoring them will not help.”