How Low Levels Of This Vitamin Impact Men’s Testosterone Levels

Testosterone levels are influenced by many factors, from sleep and exercise to stress and nutrition. But one vitamin plays a particularly important role: vitamin D.

Vitamin D receptors are highly concentrated in the testes—including in Leydig cells, the specialized cells responsible for producing testosterone. And studies have consistently showed an association between vitamin D status and testosterone levels. Observational studies indicate that men with adequate vitamin D levels tend to have higher testosterone levels compared with those who are deficient.

While this doesn’t mean vitamin D supplementation will automatically increase testosterone, it does suggest that maintaining healthy vitamin D levels may help support the body’s natural hormone production pathways. Researchers believe vitamin D may influence Leydig cell function and other processes involved in testosterone synthesis.

Beyond testosterone, vitamin D also supports influences sperm health, particularly sperm motility1.

Sperm motility refers to how well sperm can move and swim (an important factor for fertility). Studies consistently link sufficient vitamin D levels (often considered above 30 ng/mL) with healthier semen parameters, including total sperm motility, progressive motility (the ability to move forward effectively), and sperm morphology (the size and shape of sperm).

Some clinical trials have found that supplementing with vitamin D1 may improve sperm motility and measures of semen quality, particularly in men who begin with low vitamin D levels. While researchers are still exploring exactly how vitamin D affects sperm function, these findings suggest that maintaining adequate levels may be one piece of supporting reproductive health.

Several factors can make it harder to maintain healthy vitamin D levels, including limited sun exposure, spending most of your time indoors, living in northern climates, darker skin tone, and age.

While it is possible to get some vitamin D safely from the sun, it's not the best, or most efficient, source of the nutrient. Certain foods—including fatty fish, egg yolks, and fortified dairy products—can also provide vitamin D. Consuming these foods are great, but adequate intake of them still may not result in optimal vitamin D levels (as over 40% of Americans are still considered insufficient in the vitamin).

Because of that, supplementation is often the best, most reliable way to support healthy vitamin D status year-round. Vitamin D3 (cholecalciferol) is typically preferred over D2, as it’s more effective at raising and maintaining blood levels.