Understanding the science: Do D3 and K2 increase testosterone?

October 16, 2025 •

4 min read

A 2011 study on overweight men showed that vitamin D3 supplementation increased testosterone levels by 20% over a year. Emerging research also explores the connection between vitamin K2 and male hormone production. We examine the evidence to answer the question: Do D3 and K2 increase testosterone?

Quick Summary

Studies suggest a correlation between vitamin D3 deficiency and low testosterone, with supplementation potentially benefiting those with low levels. Evidence for vitamin K2's impact is largely from animal studies, showing promise for testicular function. The vitamins work synergistically, but a balanced diet and addressing deficiencies are key for hormonal support.

Key Points

Vitamin D3 is linked to testosterone: Numerous studies show a correlation between vitamin D3 deficiency and low testosterone levels.
D3 supplementation can help deficiencies: Taking D3 supplements can increase testosterone in individuals who are deficient, but may not have a significant effect on those with already optimal levels.
K2 evidence is primarily animal-based: Most of the research suggesting vitamin K2 boosts testosterone comes from animal studies, showing it can enhance testicular function and increase testosterone production.
K2's indirect role via osteocalcin: Vitamin K2 activates osteocalcin, a bone hormone that is also linked to testosterone regulation, providing a potential indirect mechanism.
D3 and K2 work together: The two vitamins work synergistically, with D3 aiding calcium absorption and K2 directing it to bones, supporting cardiovascular health which is vital for hormonal balance.
Holistic nutrition is essential: For optimal testosterone support, D3 and K2 should be part of a broader diet rich in other key nutrients like zinc, magnesium, and healthy fats.

The Science Behind Vitamin D3 and Testosterone

Often called the 'sunshine vitamin,' vitamin D3 is more than just a nutrient; it functions as a steroid hormone in the body. Receptors for vitamin D (VDR) are found in many tissues, including the male reproductive organs, particularly the Leydig cells in the testes, which are responsible for testosterone production. This widespread presence of VDR suggests a potential direct effect of vitamin D on testosterone synthesis.

The Vitamin D-Testosterone Connection

Numerous studies have explored the relationship between vitamin D levels and testosterone, revealing several important insights:

Link to Deficiency: Cross-sectional studies consistently show a positive correlation between low vitamin D levels and low testosterone in men. This suggests that correcting a vitamin D deficiency is a foundational step for optimizing overall hormonal health.
Supplementation Effects: Research on supplementation has yielded mixed but promising results, especially in deficient individuals. A notable one-year, placebo-controlled study with overweight men saw a significant increase in total, bioactive, and free testosterone in the group supplementing with vitamin D. However, other studies in non-deficient, healthy men have not always replicated these results, indicating that supplementation might primarily help restore levels to a healthy range rather than boosting already optimal levels.
Potential Mechanisms: Research points to a few key mechanisms through which vitamin D may support testosterone production:
- Direct stimulation of Leydig cells in the testes.
- Potential influence on luteinizing hormone (LH), which signals the testes to produce testosterone.

The Research on Vitamin K2 and Testosterone

Vitamin K2 is a fat-soluble vitamin primarily known for its role in bone and cardiovascular health. It works by activating proteins that direct calcium to the bones and keep it out of soft tissues like arteries. However, a less-known but promising body of research suggests a connection between vitamin K2 and testosterone.

K2's Influence on Male Hormones

Animal Studies: The strongest evidence for K2's impact on testosterone comes from animal studies. A 2011 Japanese rat study, for example, found that supplementing with the MK-4 form of vitamin K2 significantly increased testosterone levels in both the blood and testes, potentially by enhancing testicular function directly.
Role of Osteocalcin: Vitamin K2 activates a bone-derived hormone called osteocalcin. Activated osteocalcin has been linked to increased testosterone production, suggesting a pathway where K2 indirectly supports hormonal balance through its role in bone health.
Current Human Research: While animal studies are encouraging, large-scale human trials specifically investigating K2's effect on testosterone are limited. The current understanding is largely based on its physiological mechanisms, requiring more research to confirm the direct effect in men.

How Do D3 and K2 Work Together for Hormonal Health?

Combining vitamins D3 and K2 is popular due to their synergistic relationship, particularly concerning calcium metabolism. This partnership supports a healthy internal environment that is conducive to overall hormonal balance, including testosterone production.

Calcium Management: Vitamin D3 enhances calcium absorption, while vitamin K2 directs that calcium to its proper place in bones and teeth. This prevents calcium from accumulating in arteries, which supports cardiovascular health—a critical factor for overall vitality and hormonal function.
Systemic Support: A healthy, well-functioning cardiovascular system ensures efficient nutrient and hormone delivery throughout the body. By supporting heart health and bone strength, the D3 and K2 combination contributes to a better foundation for the body to produce and regulate hormones like testosterone.

Comparing D3 and K2 in Testosterone Support


Aspect	Vitamin D3	Vitamin K2
Primary Role for Testosterone	Directly stimulates Leydig cells and influences LH.	Indirectly supports via activated osteocalcin and potential direct testicular effects (mostly animal studies).
Research in Humans	Significant correlation between deficiency and low T. Supplementation is effective for deficient individuals.	Limited but promising. Evidence relies heavily on animal studies and plausible mechanisms.
Primary Source	Sunlight exposure, fatty fish, and fortified foods.	Fermented foods (e.g., natto), certain cheeses, and grass-fed animal products.

The Broader Context of Nutrition for Testosterone

While D3 and K2 are important, they are part of a larger nutritional picture. A holistic approach to diet is essential for optimal testosterone production:

Zinc: This mineral is crucial for testosterone production, and deficiencies have been linked to lower levels. Oysters, red meat, and beans are excellent sources.
Magnesium: Adequate magnesium intake is positively correlated with higher testosterone levels. Leafy greens, nuts, and whole grains are rich in magnesium.
Healthy Fats: The building blocks for hormones, healthy fats like those found in avocados, olive oil, and fatty fish are vital for testosterone health.
Balanced Diet: Extreme diets, like very low-fat or very high-protein plans, can negatively impact testosterone. A balanced intake of macros and a wide range of micronutrients is key.

Conclusion

Evidence suggests a clear association between vitamin D3 deficiency and low testosterone, with supplementation being an effective strategy for correcting this in deficient individuals. The role of vitamin K2 in supporting testosterone is more speculative, with most evidence coming from animal models demonstrating a link through testicular function and osteocalcin activation. While the combination of D3 and K2 provides synergistic benefits for bone and cardiovascular health, which indirectly support hormonal balance, it is critical to view them as components of a comprehensive nutritional approach rather than standalone 'testosterone boosters'. For best results, individuals should ensure a balanced diet, address any known deficiencies, and consult a healthcare professional to determine the appropriate course of action for their specific health needs.

Frequently Asked Questions

Vitamin D3 acts like a steroid hormone and receptors for it are found in the male testes. Studies show that adequate vitamin D levels support healthy testosterone production, possibly by directly stimulating the Leydig cells in the testes.

Animal studies suggest vitamin K2, particularly the MK-4 form, can enhance testicular function and increase testosterone production. It also activates osteocalcin, a hormone involved in bone and testosterone regulation.

Yes, taking D3 and K2 together is beneficial. Vitamin D3 helps with calcium absorption, while K2 ensures that calcium is directed to the bones and not deposited in soft tissues like arteries, promoting overall health that supports hormonal balance.

If you are deficient in vitamin D, supplementation may lead to a significant increase in your testosterone levels. However, if your levels are already optimal, supplementation is unlikely to cause a large increase. The effects of K2 are less clear in humans, but potential benefits exist.

Other important nutrients for testosterone include zinc, found in oysters and red meat; magnesium, found in leafy greens and nuts; and healthy fats from sources like avocados and fatty fish.

Good sources of vitamin D3 include sunlight, fatty fish like salmon, and fortified foods. For vitamin K2, sources include fermented foods like natto, hard cheeses, and egg yolks from grass-fed animals.

Yes, consulting a healthcare professional and getting a blood test to check for nutrient deficiencies is recommended before starting any new supplement regimen. This helps determine if you have a deficiency that could be impacting your hormone levels.