Can a vitamin B12 deficiency cause erectile dysfunction? It has not been shown to — and neither has too much B12. Low B12 is not among the causes of erectile dysfunction named by healthdirect, Healthy Male or Australian Prescriber, and studies comparing men's blood levels point in different directions. healthdirect sets no upper limit for B12. Low B12 is still worth treating — for the nerves and the blood, not as an erection fix.

What have studies found about B12 and erections?

Mixed results, all from studies that compare groups rather than test a treatment. Among 136 men, average age 63, with no other cause for ED, the 32 with low B12 had erection scores no different from the rest (Keleş et al., Andrology 2024). Two smaller studies, of 184 and 126 men, found lower B12 in men with ED than in healthy men (Xu et al., Andrologia 2021; Xu et al., Sex Med 2023), while a survey of 1,381 men in China found B12 slightly higher in men with ED (Chen et al., BMJ Open 2019).

The only randomised trial we found gave 27 men a form of B12 (mecobalamin, 1,500 micrograms a day) for six months after nerve-sparing prostate cancer surgery and compared them with 27 who did not take it: sexual function recovered no differently (Matsushita et al., 2009). No trial has tested B12 as a treatment for ED in general (PubMed search, 26 September 2026).

Does homocysteine link B12 to ED?

Possibly, but it is unproven. A 2025 meta-analysis of 12 studies — 1,766 men with ED and 2,340 without — found higher blood homocysteine in the men with ED, but also publication bias, and called for larger, more rigorous studies (Cheng et al., Int J Impot Res 2025). In one of the studies above, men with lower B12 and folate tended to have higher homocysteine (Xu 2021). A pattern in blood tests does not show that low B12 causes ED, or that raising it helps.

Who runs low on B12, and how does it show?

B12 deficiency is the most common vitamin B deficiency in Australia. It shows as tiredness and weakness, anaemia, numbness or tingling in the hands and feet, and memory or balance problems. You are at higher risk if you are an older adult, eat a vegetarian or vegan diet, have pernicious anaemia, take certain medicines such as metformin or a proton pump inhibitor, or have had bariatric surgery. Left untreated, it can cause permanent nerve damage (healthdirect — Vitamin B deficiency). Nerve problems are among the causes of ED that healthdirect lists, but none of the sources here shows B12 deficiency causing ED that way. On metformin and ED tablets together, see can metformin be taken with Viagra?

Can too much B12 cause erection problems?

There is no evidence that it does. healthdirect gives no upper limit for B12 and lists no health risk from too much (healthdirect — Vitamin B and your health); the slightly higher B12 in the Chinese survey is a blood-level pattern, not a harm shown from supplements. The B vitamins that do have limits are the others often sold alongside it: vitamin B6 (50 mg a day; nerve damage when taken at high doses for more than a year), niacin (35 mg a day as nicotinic acid; flushing, tingling, headaches and dizziness) and folate (1,000 micrograms a day; high levels can cause or worsen a B12 deficiency). healthdirect's advice is not to double up: if you take a multivitamin, check it before adding a separate B supplement.

Should you take B12 for erections?

Only if a blood test shows you are low. A vitamin B12 blood test needs a doctor's referral, and if you already take B12 you should not take it before the test (healthdirect — Vitamin B12 blood test). A deficiency is treated with the vitamin that is lacking, by injection, tablet, liquid or nasal gel or spray, and your doctor may check again after three months; the Australian Dietary Guidelines advise vegans to take a B12 supplement (healthdirect — Vitamin B deficiency). If you take an ED medicine, both Australian leaflets ask you to tell your doctor or pharmacist about vitamins and supplements, including those bought at a supermarket or health food shop (Viagra CMI; Cialis CMI). The vitamins with trial evidence for ED itself, niacin among them, are compared in the best vitamins and supplements for erectile dysfunction.

What about vitamin D, folic acid and anaemia?

Each has its own page: can a vitamin D deficiency cause ED?, does folic acid have any effect on erectile dysfunction? and, because low B12 can cause anaemia, can low iron or anaemia cause erectile dysfunction? What causes most ED is physical — reduced blood flow, nerve and hormone problems, some medicines, alcohol and smoking — and sometimes stress or anxiety (healthdirect).

The short answer

Neither low nor high B12 has been shown to cause erection problems. Low B12 is more likely in older men, vegans and people on metformin, and worth treating for your nerves and blood — but it is not an erection fix. If erections change, see your GP about the usual causes. More in our guide to lifestyle and erectile dysfunction.