Male Fertility: What Actually Improves Sperm Quality

The honest picture, with numbers

Male factors are not a footnote in fertility. NICE's Clinical Knowledge Summary on infertility gives the UK breakdown: factors in the man cause infertility in about 30% of couples, ovulatory disorders in about 25%, tubal damage in about 20%, and uterine or peritoneal disorders in about 10%. About 25% of couples have no identifiable cause. Crucially, disorders in both partners have been reported in about 40% of couples with fertility problems — which is why testing one partner and stopping there so often wastes months.

A semen analysis is one non-invasive test that removes a large share of the uncertainty. NICE guideline NG257 compares the result against the World Health Organization reference values:

Two things about that table matter more than the numbers themselves. First, these are reference values from a population of men whose partners conceived within a year — they are not a pass mark. A result below one of them lowers the odds; it does not close the door. Second, NICE notes the ranges are only valid for semen analysis carried out by the WHO method, so a mail-order home kit reporting "normal" against its own scale is not the same test.

If a first analysis is abnormal, NICE says offer a repeat confirmatory test, ideally 3 months later, because that is roughly how long a cycle of sperm formation takes. That single fact governs everything below: nothing you change today shows up in a result before about three months have passed.

What actually affects it

The things with guideline-grade evidence

NG257 is unusually specific about what to tell men who are concerned about their fertility:

• Alcohol. Excessive intake is detrimental to semen quality. Drinking within the UK Chief Medical Officers' low-risk guidance — 14 units a week, spread across several days, for example up to 2 units a day — is unlikely to affect semen quality. That is a more useful sentence than "cut out alcohol", because it tells you where the line actually sits.
• Smoking. There is an association between smoking and reduced semen quality, although NICE is careful to say the impact on male fertility itself is uncertain. NICE recommends actively supporting people to stop.
• Weight. A BMI of 30 or over carries an increased risk of reduced fertility.
• Heat. There is an association between elevated scrotal temperature and reduced semen quality — but NICE states plainly that it is uncertain whether wearing loose-fitting underwear improves fertility. The association is real; the intervention is unproven.
• Occupation. Some jobs involve exposure to hazards that reduce fertility. NICE tells clinicians to ask about occupation and, where relevant, refer to occupational health.
• Drugs. NICE names testosterone-replacement therapy, finasteride, GLP-1 agonists, anabolic steroids and cannabis as worth asking about specifically. Testosterone in particular suppresses sperm production; men are often surprised by this, because it is prescribed and marketed as a virility treatment.

Varicocele

A varicocele — enlarged veins in the scrotum — is present in roughly 15% of the general male population, in 25% of men with an abnormal semen analysis, and in 35–40% of men presenting with infertility. NG257 recommends considering radiological or surgical treatment for men with a varicocele detected on clinical examination who are trying to conceive spontaneously and have reduced semen parameters. This is one of the few genuinely modifiable structural causes, and it is found on a physical examination — which is why NICE says to offer scrotal and testicular examination to anyone with two or more abnormal semen analyses.

Supplements and antioxidants: read this before you buy anything

The supplement aisle for male fertility is large, expensive and largely unregulated. The best available synthesis is a 2022 Cochrane review of antioxidants for male subfertility covering 90 studies and 10,303 men. It found antioxidants may increase live birth (odds ratio 1.43, 95% CI 1.07 to 1.91) — but rated that as very low-certainty evidence from just 12 trials and 1,283 men. When the trials at high risk of bias were excluded, the effect disappeared (OR 1.22, 95% CI 0.85 to 1.75). Gastrointestinal upset was more common on antioxidants (OR 2.70, 95% CI 1.46 to 4.99). The authors' own conclusion is that the evidence is inconclusive.

NICE goes further and makes it a recommendation: do not offer supplements, antioxidants or medical treatments to improve sperm DNA integrity. NICE also says do not carry out testing for sperm DNA fragmentation at all — which matters because that test is frequently the sales route into an antioxidant package.

What is not recommended

NG257 also says: do not offer routine antisperm antibody testing; do not offer androgens to treat semen abnormalities; do not offer antibiotics for leukocytes in semen unless there is an identified infection; and only consider gonadotrophin or anti-oestrogen therapy for men with impaired semen parameters and no hypogonadotropic hypogonadism as part of a clinical trial. Where hypogonadotropic hypogonadism is diagnosed, gonadotrophin therapy is offered — that is a real, effective treatment for a specific diagnosis, not a general tonic.

What to do next

1. Get a semen analysis, early and through a laboratory using the WHO method. In the UK this is arranged through a GP. It is one sample and it changes the whole plan.
2. If the first result is abnormal, expect a repeat at about 3 months — unless azoospermia or severe oligozoospermia is found, in which case NICE says repeat as soon as possible rather than waiting.
3. Ask for a physical examination if two analyses are abnormal. NICE recommends scrotal and testicular examination, and consideration of serum testosterone and gonadotrophin levels.
4. Stop testosterone or anabolic steroids and tell the clinician you were taking them. This is common, it is fixable, and concealing it wastes the investigation.
5. Do the low-cost, evidence-backed things: stay within 14 units of alcohol a week spread over several days, stop smoking with real support, address a BMI of 30 or over, and have intercourse every 2 to 3 days rather than saving up.
6. Do not buy a sperm DNA fragmentation test or an antioxidant stack on the strength of a clinic's marketing. Ask what NICE says about both.

When to seek help

NICE recommends further assessment and investigation of both partners after 1 year of unprotected vaginal intercourse — and referral at first presentation if the woman trying to conceive is 36 or over, or if either partner has a known or suspected clinical cause of infertility or a history of predisposing factors. Previous testicular surgery, undescended testes, testicular torsion or trauma, mumps orchitis, chemotherapy or radiotherapy, or a known chromosomal condition all count as predisposing factors. So does a previous partner's failure to conceive.

Go sooner, not later, if there is a history of cancer treatment, if either testis has been operated on, or if you have been on testosterone.

Where the count is very low or absent, NG257 sets out a defined genetic pathway rather than guesswork: Y chromosome microdeletion testing for idiopathic azoospermia or a concentration below 1 million per ml; cystic fibrosis (CFTR) testing for suspected obstructive azoospermia or a vasal abnormality; karyotype testing for idiopathic azoospermia, and consideration of it for a persistent concentration below 5 million per ml. Genetic counselling is offered where a specific defect is found. Azoospermia is not the end of the conversation — NICE recommends surgical correction or surgical sperm retrieval for obstructive azoospermia, and surgical sperm retrieval, considering micro-TESE, for non-obstructive azoospermia.

A note on how this gets framed

Fertility is still discussed as though it were a woman's problem with a male afterthought, and the practical result is that semen analysis is often the last test ordered rather than the first. It is cheap, quick and non-invasive, and it is involved in around 30% of cases on its own and 40% in combination. If you take one thing from this page, make it the sequencing: test both partners at the same time, not one after the other.