Testosterone replacement therapy does not raise blood sugar. In most men, particularly those with low testosterone, TRT tends to improve blood sugar control by reducing insulin resistance. A meta-analysis of randomized controlled trials in men with type 2 diabetes and low testosterone found that TRT lowered HbA1c by an average of 0.87 percentage points, reduced fasting blood glucose, and decreased fasting insulin levels.
That said, the relationship between testosterone and blood sugar is more nuanced than a simple “it helps.” How much benefit you see, how quickly it happens, and whether it creates any risks depends on your starting point, your dose, and whether you’re already taking diabetes medications.
How Testosterone Affects Blood Sugar
Testosterone influences blood sugar through at least two pathways. The first is direct: testosterone modulates the expression of a glucose transporter called GLUT4 and the insulin receptor in both muscle and fat tissue. These are the molecular doorways that let sugar move from your bloodstream into your cells. When they work better, your body clears glucose more efficiently. This effect appears to be independent of body composition, meaning testosterone improves insulin sensitivity even beyond what you’d expect from changes in weight or muscle mass.
The second pathway is indirect. TRT consistently increases lean body mass (by roughly 1.9 kg in clinical trials) while reducing body fat. Since muscle is the primary tissue responsible for absorbing glucose from your blood after a meal, having more of it gives your body a larger “sink” for blood sugar. Less body fat also reduces the chronic low-grade inflammation that drives insulin resistance in the first place.
What the Numbers Show in Diabetic Men
The strongest evidence comes from men who have both type 2 diabetes and clinically low testosterone. In these men, meta-analyses consistently show improvements across several blood sugar markers. One systematic review found TRT reduced fasting plasma glucose by a mean difference of 1.10 mmol/L, fasting insulin by 2.73 units, and HbA1c by 0.87 percentage points compared to placebo. A separate, more recent meta-analysis confirmed a statistically significant HbA1c reduction of 0.29 percentage points, though with considerable variation between studies.
Insulin resistance scores (measured by HOMA-IR, a calculation based on fasting glucose and insulin) also improved across multiple trials. The direction of the effect is clear and consistent: testosterone therapy lowers blood sugar markers in hypogonadal men with diabetes, not raises them.
How Quickly Blood Sugar Changes
Insulin sensitivity can begin improving within days of starting TRT. One study documented reduced fasting glucose and insulin within a single week, and earlier research showed measurable changes in insulin sensitivity within 48 hours of boosting testosterone levels. However, the clinically meaningful improvements in blood sugar control, the kind that show up on an HbA1c test, take longer to materialize.
Most studies report noticeable HbA1c reductions by 3 months, with further declines continuing through 12 months. If you’re tracking your blood sugar at home, you may see fasting glucose trending downward within the first few months, but it takes a full quarter or more before the cumulative effect is large enough to register on lab work.
The Hypoglycemia Risk for Diabetics
Here’s the practical concern most people miss: if TRT lowers blood sugar and you’re already taking diabetes medications, the combination can push your blood sugar too low. Testosterone can enhance the glucose-lowering effect of insulin and certain oral medications, particularly sulfonylureas (the class of drugs that stimulate your pancreas to produce more insulin). This creates a real risk of hypoglycemia, episodes of dangerously low blood sugar that cause shakiness, confusion, and in severe cases, loss of consciousness.
Metformin carries less risk in this scenario because it works by sensitizing your body to insulin rather than forcing more insulin production. It doesn’t typically cause hypoglycemia on its own, even at high doses. But if you’re on insulin injections or sulfonylureas alongside TRT, your treating physician may need to reduce your diabetes medication doses as your insulin sensitivity improves. Monitoring blood sugar more frequently in the first few months of TRT is a practical way to catch this early.
What About Supraphysiological Doses
There’s a meaningful distinction between therapeutic TRT (which brings testosterone into the normal physiological range) and the much higher doses used in bodybuilding or performance enhancement. You might expect that if normal testosterone improves blood sugar, more would be even better, but research on recreational bodybuilders using anabolic steroids at supraphysiological doses found that hormonal abuse did not significantly affect fasting plasma insulin or glucose concentrations. The metabolic benefits seen with TRT didn’t scale upward with higher doses, and there were theoretical concerns about insulin resistance from shifts in muscle fiber type composition.
Growth hormone, which is often stacked with anabolic steroids in bodybuilding, is a different story. Supraphysiological growth hormone doses can directly cause insulin resistance and increase type 2 diabetes risk. If someone reports worsening blood sugar while using performance-enhancing drugs, growth hormone or other compounds in the stack are more likely culprits than testosterone itself.
Why Guidelines Still Urge Caution
Despite the favorable data on blood sugar, the Endocrine Society explicitly recommends against using TRT as a treatment for improving glycemic control in men with type 2 diabetes. This isn’t because TRT worsens blood sugar. It’s because the improvements, while statistically significant in studies, are modest and variable. The HbA1c reductions are smaller than what diet changes, exercise, or standard diabetes medications achieve. And TRT carries its own risks, including increased red blood cell production that requires regular monitoring.
The standard monitoring protocol for men on TRT does not include routine glucose or HbA1c checks. Men with type 2 diabetes on TRT follow the same monitoring plan as any other man on testosterone therapy, with the added expectation that their diabetes care continues as usual. The takeaway: TRT can be a helpful tailwind for blood sugar control if you happen to need it for low testosterone, but it’s not a diabetes treatment on its own.