Testosterone tends to get discussed in terms of muscle, energy, and libido, while blood sugar gets filed under a completely separate topic reserved for diabetes conversations. Research over the past two decades suggests that filing them separately misses something important. Testosterone and blood sugar regulation appear to influence each other in both directions, and the connection has real implications for how a man might think about either one.
How Low Testosterone Is Linked to Insulin Resistance
Insulin resistance is a condition in which the body’s cells respond less effectively to insulin, the hormone that moves glucose out of the bloodstream and into cells for energy. Over time, insulin resistance is a major driver of type 2 diabetes. A study of 60 men across the full range of glucose tolerance found a clear positive relationship between testosterone levels and insulin sensitivity, measured using the gold-standard clamp technique. Men with hypogonadal, meaning clinically low, testosterone levels were about twice as insulin resistant as men with normal levels (Pitteloud et al., 2005, Diabetes Care).
A Possible Role for Mitochondria
That same study offered a clue about why this might happen. The researchers found that low testosterone was associated with reduced mitochondrial function in muscle tissue, the cellular machinery responsible for turning fuel into usable energy. Since impaired mitochondrial function is itself linked to insulin resistance, this offers one plausible mechanism connecting the two conditions, though it’s not the only one researchers have proposed.
Does Low Testosterone Predict Future Diabetes Risk?
Beyond a snapshot association, several long-term studies have tracked men over years to see whether testosterone levels predict who later develops type 2 diabetes. A meta-analysis pooling 13 cohort and nested case-control studies found that men with higher total testosterone had a significantly lower risk of developing type 2 diabetes over follow-up periods, compared with men who had lower levels (Yao et al., 2018, Endocrine Connections). A separate five-year prospective study of more than 1,600 Australian men found that low serum testosterone predicted an increased risk of developing type 2 diabetes, independent of other established risk factors already used in clinical diabetes risk assessments (Atlantis et al., 2016, BMC Endocrine Disorders).
The Relationship Isn’t as Simple as It First Appears
What makes this topic more complicated, and more interesting, is that the direction of cause and effect isn’t as settled as it might seem. A Swedish population study that followed more than 1,200 men over roughly a decade tested this directly: did low testosterone predict later insulin resistance, did insulin resistance predict later low testosterone, or both? The researchers found that low testosterone at the start of the study did predict higher insulin resistance about a decade later. But the reverse did not hold in this particular study: baseline insulin resistance did not significantly predict lower testosterone at follow-up (Ottarsdottir et al., 2018, Endocrine Connections). That’s a more one-directional finding than the popular “vicious cycle” framing often suggests, even though other cross-sectional and mechanistic research does support effects running in both directions. It’s a good example of how the full picture in this area is still being worked out, and why it’s worth being specific about what a given study actually found rather than reaching for the most dramatic version of the story.
Why This Might Happen
A few overlapping mechanisms have been proposed. Excess body fat, particularly visceral fat around the abdomen, is closely linked to both insulin resistance and lower testosterone, since fat tissue contains an enzyme that converts testosterone into estrogen and also promotes chronic low-grade inflammation that interferes with normal hormone signaling. Testosterone itself appears to influence pancreatic insulin secretion and skeletal muscle’s ability to take up glucose, which is part of why replacing testosterone in men with clinically low levels has, in some but not all studies, shown modest improvements in insulin sensitivity.
What This Means in Practical Terms
None of this means every man with a slightly elevated blood sugar reading or a slightly lower testosterone level is caught in some inevitable downward spiral. It does mean the two systems are more connected than they’re often treated as being. If you’ve had bloodwork showing borderline insulin resistance or prediabetes, it may be worth asking your doctor whether a testosterone check makes sense as part of the picture, and the reverse holds too. A man dealing with low testosterone symptoms has a reasonable case for asking about metabolic markers like fasting glucose or HbA1c rather than assuming the two issues are unrelated.
The other practical takeaway is that the same lifestyle changes tend to help both. Losing excess body fat, particularly visceral fat, and building consistent physical activity into a routine are well supported for improving insulin sensitivity, and there’s reasonable evidence that meaningful weight loss can raise testosterone levels in men who were carrying excess weight to begin with.
Frequently Asked Questions
A few common questions on this topic, based on what current research actually supports.
Does Low Testosterone Cause Insulin Resistance, or the Other Way Around?
Both directions have support in the research, but the strongest longitudinal evidence points to low testosterone predicting future insulin resistance more consistently than the reverse.
Can Low Testosterone Predict Future Diabetes Risk?
Yes. Multiple long-term studies have found that men with lower testosterone levels have a higher likelihood of developing type 2 diabetes over years of follow-up, independent of other known risk factors.
Will Raising My Testosterone Improve My Blood Sugar?
Some studies on testosterone therapy have shown modest improvements in insulin sensitivity in men with clinically low testosterone, though results have been inconsistent across studies.
Should I Get Both Tested If I’m Concerned About One?
It’s a reasonable question to raise with a doctor, since the two conditions are closely connected and addressing one may be relevant to the other.
