Testosterone is a sex hormone that regulates a number of processes in the human body, including fertility, sex drive, bone mass, fat distribution, muscle mass, and red blood cell production. Testosterone levels typically decrease as you age, but for some people, these levels can become too low and cause unwanted symptoms.

Diabetes is a condition in which the body is unable to process blood glucose, also known as blood sugar.

While a link between low testosterone and diabetes isn’t immediately obvious, researchers have discovered that the two are connected. According to the American Diabetes Association (ADA), if you have diabetes, you’re twice as likely to have low testosterone than people who don’t have diabetes.

Insulin is a hormone released by the pancreas after you eat a meal. This hormone tells your cells to pick up sugar from the blood.

Studies suggest that low testosterone levels correspond with higher insulin resistance in people assigned male at birth (AMAB). Insulin resistance occurs when your cells stop responding to the insulin. This means that glucose (sugar) is taken up by the tissues at a much slower rate.

Researchers are still trying to understand the role that low testosterone plays in developing insulin resistance. Testosterone likely plays a role in a signaling pathway responsible for glucose uptake into the cells.

Therefore, if you have lower-than-standard testosterone levels, blood sugar levels rise after eating a meal and stay high for a longer period of time. In other words, for AMAB people, having low testosterone can raise your blood sugar levels.

There’s a clear relationship between low testosterone and insulin resistance. This also establishes a clear link between low testosterone and type 2 diabetes.

If you have insulin resistance, your body will have to make extra insulin to keep blood sugar levels normal. Over time, the pancreas — the organ responsible for producing insulin — can’t keep up with the increased demand.

Type 2 diabetes occurs when the pancreas can’t make enough insulin to overcome insulin resistance. Once you have diabetes, excess glucose (sugar) in the blood (also known as hyperglycemia) begins to circulate and cause damage throughout the body.

Testosterone may improve insulin resistance in people with diabetes, but it’s important to talk with a doctor about the risks of taking testosterone therapy.

An older 2006 study assessed the use of testosterone replacement therapy (TRT) in men with type 2 diabetes and low testosterone. The study found that taking TRT improved blood sugar control, insulin resistance, cholesterol levels, and visceral fat.

Likewise, a more recent 2020 study in 356 men with type 2 diabetes and low testosterone found that long-term treatment with TRT improved both glycemic control and insulin resistance. On top of this, one-third of the men in the study experienced a remission of their diabetes, and a majority of the study participants reached their target level of HbA1c (average blood sugar level over the past few months).

In another study in mice, researchers were able to pinpoint how testosterone triggers key signaling pathways in cells of the pancreas that produce insulin. This research may help scientists understand if the hormone can potentially be used to treat diabetes.

More research, including well-controlled, long-term clinical trials, will be needed to determine if TRT can improve insulin resistance and help treat diabetes in people with low testosterone. It’s currently not clear if the benefits of TRT outweigh its risks.

Some doctors do not advise prescribing TRT to people younger than 65 years of age, even if they have low testosterone levels, since the long-term risks aren’t well understood.

Testosterone therapy in AFAB people with diabetes

Testosterone is often referred to as a male sex hormone because testosterone levels are typically much higher in AMAB people compared with people assigned female at birth (AFAB).

Some AFAB people can have elevated levels of testosterone caused by an underlying condition, such as polycystic ovary syndrome (PCOS). Though insulin resistance is associated with low testosterone levels in AMAB people, it’s associated with higher-than-normal testosterone levels in AFAB people.

AFAB people undergoing gender-affirming therapy (such as transgender men) often take TRT as part of the transition process, which increases their testosterone levels. The use of TRT as part of gender-affirming therapy doesn’t appear to have an effect on insulin resistance.

A systematic review of 26 studies found that TRT increased lean mass and decreased fat mass but had no impact on insulin resistance in AFAB people. Likewise, a large retrospective study of 2,585 transgender women and 1,514 transgender men receiving gender-affirming hormone therapy found no difference in risk of type 2 diabetes between transgender women and men compared with the general population of cisgender adults.

More research is needed to further understand the impact of testosterone therapy on insulin resistance.

Talk with a doctor if you’re experiencing any of the symptoms of low testosterone, such as decreased sex drive, fatigue, decreased muscle mass, mood changes, and difficulty achieving an erection. Your doctor can check your testosterone levels with a blood test.

If you also have diabetes, ask your doctor if low testosterone and your diabetes could be related and if TRT could help treat both conditions. If you decide to treat low testosterone with hormone replacement therapy, be sure to discuss with your doctor how this might affect your diabetes treatment.

Keep in mind that TRT can cause side effects, including:

Some older studies have shown that TRT could lead to an increased rate of stroke and heart attack, but this is controversial. It’s important to discuss the risks and benefits of testosterone replacement with your doctor.

Along with diabetes medications, your doctor may recommend other ways of lowering your blood sugar, such as:

  • certain diet changes, such as eating more vegetables and cutting back on sugar
  • an exercise program, such as walking or other low impact exercises
  • lowering alcohol intake

Ask a doctor to refer you to a dietitian or nutritionist who specializes in people with diabetes, so they can design a treatment plan that’s right for you.

Researchers have established a clear link between low testosterone, increased insulin resistance, and diabetes. Though studies have shown that TRT may prevent or possibly treat diabetes in men with low testosterone, more research is needed to confirm if the benefits of TRT outweigh the risks.

If you have low testosterone, diabetes, or both, speak with a doctor to understand the connection and how this might impact your treatment plan.