Educational content, not medical advice. Testing and treatment decisions belong with a physician.
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The link runs both ways
Low testosterone and insulin resistance travel together. Men with abdominal obesity, metabolic syndrome or type 2 diabetes more often have low levels, and men with low testosterone are at higher risk of developing diabetes later. The relationship probably runs in both directions. Fat tissue converts testosterone to estrogen and sends signals that dampen the brain's control of the testes. In turn, testosterone helps decide how much muscle and how much belly fat the body carries, and therefore how well it handles sugar.
So the clinical question is not whether there is a link. There is. The question is whether treating the hormone changes the metabolic disease.
How common is low testosterone in type 2 diabetes?
Dhindsa and colleagues (JCEM, 2004) studied men with type 2 diabetes and found that about one in three was hypogonadal, most with low LH and FSH. That means the signal from the brain was low, not that the testes were diseased. Other surveys give other figures because the thresholds differ. Read why prevalence depends on the criteria in our note on the EMAS study.
Controlled evidence
A later placebo-controlled trial (Dhindsa et al., Diabetes Care 2016) included 94 men with type 2 diabetes. 44 of them had hypogonadotropic hypogonadism and were randomised to testosterone or placebo. After 24 weeks, insulin sensitivity measured by euglycaemic clamp had risen by 32% in the testosterone group. Subcutaneous fat fell by about 3.3 kg and lean mass rose by about 3.4 kg, while visceral and liver fat did not change. The trial was small and short, so it shows a mechanism rather than a long-term effect.
T4DM (Wittert et al., Lancet Diabetes & Endocrinology 2021) is the largest trial in the field. 1,007 men aged 50–74 with a waist of at least 95 cm, total testosterone of 14 nmol/L or lower and either impaired glucose tolerance or newly diagnosed type 2 diabetes all joined a lifestyle programme. They were then randomised to testosterone undecanoate injections or placebo for two years. After two years, 12% in the testosterone group had type 2 diabetes on a glucose tolerance test versus 21% in the placebo group (relative risk 0.59). The effect came on top of the lifestyle programme and did not depend on baseline testosterone. Read the full walkthrough on the T4DM study page.
Registry data
Haider and colleagues (Diabetes, Obesity and Metabolism 2020) followed 356 men with type 2 diabetes and total testosterone of 12.1 nmol/L or lower in a registry for up to eleven years. Of those treated, 34.3% achieved remission of their diabetes, while values rose in the comparison group. A registry is not randomised. Treated and untreated men may have differed in other ways, so the figures show an association, not proof.
What does it mean for you?
Testosterone is not a replacement for lifestyle. In T4DM every participant had a lifestyle programme, and that is what makes the result credible. Weight loss, exercise and sleep on their own raise testosterone in many men with overweight. Treatment is only relevant for symptomatic deficiency and always together with a doctor.
The caveats are real. In T4DM, 22% in the testosterone group had haematocrit above 54% versus 1% on placebo, and the trial was not powered to assess cardiovascular events. Haematocrit and PSA must therefore be monitored if treatment is started.
How it is measured
The American Diabetes Association (ADA) recommends in its Standards of Care measuring morning testosterone in men with diabetes who have symptoms or signs of low testosterone. The Endocrine Society (Bhasin et al., JCEM 2018) recommends a fasting morning sample, repeated to confirm a low result. Measure total testosterone, SHBG and ideally LH and FSH in the same sample.
First step
If you are in one of the relevant groups and are worried that low testosterone may be a contributing factor, a screening may be an option. Talk to your own doctor about the options. If you want fast action via a private clinic, you are welcome to take the free AMS test on this site, or, if you are in Denmark, order a blood test.
Questions & answers
Is low testosterone common in type 2 diabetes?
Yes. Studies have found low testosterone in roughly a third of men with type 2 diabetes, often a secondary pattern linked to excess weight.
Can testosterone treatment prevent diabetes?
In the T4DM trial, testosterone added to a lifestyle programme reduced the share of men who developed type 2 diabetes compared with lifestyle alone. It is not approved for that purpose.
What helps first?
Weight loss, exercise and better sleep can raise testosterone and improve insulin sensitivity. Any treatment decision is individual and made with a physician.