Gram Research analysis of 82 men with varicoceles found that those with the most severe grade had lower vitamin D in the vein draining the testicle, averaging 29.9 ng/mL versus 32.3 ng/mL in an arm vein. Overall vitamin D levels were similar in both veins. Researchers say more work is needed before this changes care.
Varicoceles are swollen veins inside the scrotum that can affect male fertility. A new study reviewed by Gram Research analysis looked at vitamin D levels in 82 men with varicoceles who were scheduled for surgery. Researchers measured vitamin D in the vein that drains the testicle and in a vein in the arm. Overall, the levels were similar in both veins, averaging about 32 ng/mL. However, men with the most severe type of varicocele (Grade III) had lower vitamin D in the testicle vein, at 29.9 compared to 32.3 ng/mL in the arm vein. Vitamin D also showed a weak link to sperm concentration. The study was small and only observed a single point in time, so it cannot prove that low vitamin D causes problems. Still, it suggests vitamin D may be part of how severe varicoceles affect the testicles.
Key Statistics
A 2026 observational study of 82 men with varicoceles found that men with the most severe Grade III varicoceles had vitamin D averaging 29.9 ng/mL in the left spermatic vein, compared to 32.3 ng/mL in a peripheral vein.
In the same 2026 study of 82 men, sperm concentration showed a weak positive correlation with vitamin D in the peripheral vein (r = 0.23, P = 0.040).
The Quick Take
- What they studied: Researchers wanted to know whether vitamin D levels differ between the vein that drains the testicle and a vein in the arm in men with varicoceles, and whether those levels relate to how severe the varicocele is and to sperm quality.
- Who participated: The study included 82 men with varicoceles, which are enlarged veins inside the scrotum. Their average age was about 32 years. All were scheduled for surgery to tie off the enlarged veins.
- Key finding: Vitamin D levels were similar in both veins across all men. But men with the most severe varicoceles (Grade III) had noticeably lower vitamin D in the testicle vein, about 29.9 compared to 32.3 ng/mL in the arm vein. This difference was statistically significant, meaning it was unlikely to be due to chance alone. Vitamin D also showed only a weak connection to sperm count.
- What it means for you: If you have a varicocele, this study does not mean you should change your vitamin D intake or start supplements. It adds a piece to the puzzle about how severe varicoceles may affect the testicles. Talk with a urologist or fertility specialist about your own vitamin D level and your options.
The Research Details
This was an observational study, which means the researchers watched and measured what was already happening in patients rather than assigning them to receive a treatment. All participants had varicoceles and were scheduled for a surgery called varicocelectomy, in which the enlarged veins are closed off.
Before surgery, doctors collected routine information, including blood levels of vitamin D, calcium, and a hormone called parathyroid hormone. They also ran a semen analysis, which checks sperm count and quality. During the operation, the surgeons drew a small blood sample from the left spermatic vein, the vein that carries blood away from the left testicle, before closing it. This allowed a direct comparison with blood drawn from a peripheral vein, which is a vein elsewhere in the body.
The researchers then compared vitamin D levels between the two veins, looked at how these levels changed with varicocele severity, and checked whether they tracked with sperm measurements. Because all of this was gathered at one moment in time, the study can show that things are connected, but not which one causes the other.
Comparing blood from the testicle vein with blood from a nearby or distant vein lets researchers see what is happening locally in the testicle, not just in the general bloodstream. Measuring both veins in the same person at the same time reduces the chance that other differences between people explain the results. Grouping patients by varicocele grade also helped reveal that the difference appeared only in the most severe cases.
This study was published in a peer-reviewed medical journal, which means other experts reviewed it before publication. It measured both blood levels and semen quality in the same patients, which adds useful detail. However, the sample of 82 men is modest, and the study looked at only one moment in time. The number of men with Grade III varicoceles was not clearly reported in the summary, and the sperm link was weak. Results from a single study should be confirmed by larger, longer studies before they are used to guide care.
What the Results Show
Across all 82 men, vitamin D levels were similar in the two veins. In the peripheral vein, the average was 32.9 ng/mL, with a standard deviation (a measure of how spread out the numbers are) of 9.6. In the left spermatic vein, the average was 31.9 ng/mL, with a standard deviation of 10.5. The difference between these two averages was small and not statistically significant.
The picture changed when researchers looked only at men with the most severe varicoceles. In men with Grade III varicoceles, vitamin D in the left spermatic vein was 29.9 ng/mL, compared to 32.3 ng/mL in the peripheral vein. This gap was statistically significant (P = 0.032), meaning it was unlikely to have happened by chance. Men with milder varicoceles did not show this gap.
For context, a difference of about 2 to 3 ng/mL is modest in everyday terms. Still, it was consistent enough within the most severe group to draw the researchers’ attention. The study suggests that severe varicoceles may be linked to lower vitamin D in the vein that drains the testicle.
The researchers also checked whether vitamin D levels were related to semen quality. Sperm concentration, meaning how many sperm are present in a sample, showed a weak positive connection with vitamin D in the peripheral vein (correlation r = 0.23, P = 0.040). The link in the spermatic vein was similar in direction but did not reach the usual threshold for significance (r = 0.21, P = 0.06).
The weak correlations mean that higher vitamin D tended to go along with higher sperm concentration, but vitamin D explains only a small portion of the variation between men. Other blood markers measured before surgery, including parathyroid hormone and calcium, did not show a meaningful relationship with semen results. Varicocele grade also did not clearly predict semen analysis results in this group.
Earlier research has suggested that varicoceles can affect the testicles by changing the local chemical environment, including markers linked to inflammation and oxidative stress. Vitamin D has been studied in relation to male reproductive health, and some studies have linked low levels with lower sperm quality. This study adds a detail that is less common: it measured vitamin D directly in the vein draining the testicle, rather than only in general blood. Its findings fit the idea that severe varicoceles may disrupt local biochemistry, though the research on vitamin D and fertility remains mixed and is still developing.
The study looked at a single point in time, so it cannot show whether low vitamin D causes varicoceles to damage sperm, or whether the damage causes changes in vitamin D. The sample of 82 men is relatively small, and the number of men in each varicocele grade was not clearly reported in the summary, which makes the Grade III result harder to judge. The semen link was weak and only borderline for one measure. The patients were all men already scheduled for surgery, so the results may not apply to men with mild varicoceles who are not having surgery. Vitamin D levels can also vary with season, diet, sun exposure, and body weight, and these factors were not described in detail in the summary.
The Bottom Line
Confidence level: low to moderate. The finding that severe (Grade III) varicoceles are linked to lower vitamin D in the testicle vein is interesting and worth further study. However, this is a single, small observational study, so it should not change treatment decisions on its own. Men with varicoceles who have fertility concerns should discuss vitamin D testing with their doctor as part of a broader evaluation. Routine vitamin D supplementation specifically for varicoceles is not supported by this research alone.
Men diagnosed with a varicocele, especially those with severe (Grade III) varicoceles or fertility concerns, may find this research relevant to discuss with their doctor. Urologists, fertility specialists, and researchers studying male reproductive health should also pay attention. Men with mild varicoceles, women, and people without vein problems are less likely to find direct practical use in these results.
Because this is a single snapshot study, it cannot tell us how long it takes for vitamin D levels to change or whether changes would affect fertility. Any future clinical use would depend on larger studies that follow men over months or years, including whether correcting low vitamin D improves sperm measures after varicocele treatment. For now, expectations should stay modest, and any changes in vitamin D levels would likely take several weeks to months to show up in blood tests.
Frequently Asked Questions
Does a varicocele affect vitamin D levels in the testicles?
A 2026 study of 82 men found that vitamin D levels were similar overall in the testicle vein and an arm vein. However, men with the most severe Grade III varicoceles had lower vitamin D in the testicle vein, at 29.9 compared to 32.3 ng/mL, suggesting a possible link that needs more research.
Is low vitamin D linked to lower sperm count?
A 2026 study of 82 men found only a weak positive connection between vitamin D and sperm concentration, with a correlation of r = 0.23 in the peripheral vein. Vitamin D explains only a small part of sperm count differences, so it is not a sole factor in fertility.
Should I take vitamin D supplements if I have a varicocele?
Current research does not show that vitamin D supplements improve varicocele outcomes or fertility. Vitamin D levels can be checked with a simple blood test, and a doctor can decide whether supplementation makes sense based on your individual results and health history.
What is a varicocele and how does it affect fertility?
A varicocele is an enlargement of the veins inside the scrotum, similar to varicose veins in the legs. Research suggests it can disrupt the chemistry around the testicles, which may affect sperm quality in some men, particularly those with more severe cases.
Want to Apply This Research?
- Log your vitamin D blood test result (in ng/mL) each time you get one, along with the date and any supplement dose you take. If you have a varicocele, also note the grade your doctor gave you and any semen analysis results, so you can see patterns over time with your care team.
- Ask your doctor whether a vitamin D blood test makes sense for you, especially if you have a varicocele and are concerned about fertility. Track any supplement you take daily, including the dose and time, and review it with your doctor before making changes. Do not start high-dose supplements without medical advice.
- Set a reminder to review your vitamin D level and semen analysis results every few months, or as your doctor recommends. Record changes alongside any treatments, such as varicocele surgery, so you and your doctor can see whether there are meaningful shifts. Share the trend data during appointments rather than relying on a single number.
This article summarizes a single observational study and is for general education only. It is not medical advice and does not replace consultation with a urologist, fertility specialist, or other qualified healthcare provider. Do not change any medication, supplement, or treatment plan based on this research without speaking to your doctor.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.