10 Sperm Killers to Avoid When Trying to Get Pregnant
When couples struggle to conceive, the focus often lands on the woman first. But male factors play a role in up to half of all fertility problems, and in about 20 to 30 percent of cases they are the only cause. The encouraging part is that sperm quality is one of the most changeable parts of fertility. Many everyday habits can harm sperm, and changing them can make a real difference.
This guide walks you through ten proven sperm killers, explains how each one affects sperm, and shows you what to do about it. If you are the partner of someone trying to conceive, share this with him. It works best as a team effort.
What Are Sperm Killers and Why Do They Matter?
A sperm killer is anything that lowers sperm count, slows sperm movement (motility), changes sperm shape, or damages the DNA inside sperm. Any of these can make it harder to conceive or can affect the health of a pregnancy.
Here is the most important fact to remember: sperm take about 74 days, roughly two and a half to three months, to develop. That means what you do today shows up in your semen about three months from now. It also means that when you remove a sperm killer, your sperm can recover, and you will usually see the benefit within one cycle of sperm production.
For a quick reference, the World Health Organization’s 2021 lower reference limits for a healthy semen sample are about 16 million sperm per milliliter, 42 percent total motility, and 4 percent normal shape. If your results fall below these numbers, one or more of the factors below may be part of the reason.
What Are the 10 Proven Sperm Killers?
1. Smoking
Smoking is one of the best documented lifestyle causes of poor sperm quality. Studies consistently link it with lower sperm count, reduced motility, and more DNA damage. Evidence on vaping is still limited, but nicotine and other chemicals may affect sperm too, so quitting completely is the safest choice. Support from a doctor or cessation program roughly doubles the chance of success.
2. Heavy Alcohol Use
Regular heavy drinking can lower testosterone, reduce sperm count, and change sperm shape. The effects of light or moderate drinking are less clear, but when you are trying to conceive, many experts recommend cutting back to a minimum. Binge drinking is the pattern most worth avoiding.
3. Too Much Heat
Your testicles hang outside your body because sperm production works best at a temperature slightly below core body temperature. Frequent hot tubs, saunas, hot baths, heated car seats, long hours of sitting, and a laptop resting on your lap can all raise scrotal temperature. Read more in our guide to how temperature affects sperm health, and if you are curious about the opposite approach, see our article on cold plunges and male fertility.
Be sure to treat a fever as heat exposure too. A high fever from an illness can lower sperm count for up to about three months.
4. Anabolic Steroids and Testosterone Therapy
This is the one that surprises people most. Taking outside testosterone or anabolic steroids tells your brain to shut down the hormones (LH and FSH) that drive sperm production. As a result, sperm count can fall dramatically, sometimes to zero. Testosterone therapy is not a fertility treatment. If you use it, or a supplement that may contain steroid like compounds, talk with your doctor before you try to conceive. Recovery is often possible but can take months.
5. Marijuana and Recreational Drugs
Regular marijuana use has been linked with lower sperm concentration, especially when combined with alcohol. Cocaine, opioids, and other recreational drugs can also reduce sperm quality and lower testosterone. If you use any of these and are trying to conceive, stopping gives your sperm the best chance to recover.
6. Excess Weight and a Poor Diet
Obesity is associated with lower testosterone, reduced sperm count, and poorer sperm quality, partly because fat tissue changes how your body handles hormones. Diets heavy in highly processed foods, processed meats, sugary drinks, and trans fats are linked with lower semen quality, while diets rich in vegetables, fruit, fish, nuts, and whole grains are linked with better results. Our fertility nutrition guide shows you how to build meals that support fertility, and our breakdown of the best fertility supplements explains which ones are worth a conversation with your doctor.
7. Chronic Stress and Poor Sleep
Long periods of stress raise cortisol, which can interfere with testosterone and sperm production. Poor or short sleep is also linked with lower sperm concentration and lower testosterone. Aim for seven to nine hours a night and build in stress relief that works for you, whether that is walking, strength training, or time outdoors. Very intense, frequent workouts can add stress as well, which is why you may relate to why Katy stopped doing high intensity workouts.
8. Environmental Toxins
Pesticides, certain plastics (such as BPA and phthalates), PFAS chemicals, heavy metals such as lead and cadmium, industrial solvents, and air pollution have all been linked with reduced sperm quality. People who work with chemicals, in farming, welding, painting, or manufacturing may have higher exposure. Practical steps include:
- Wash fruits and vegetables well
- Avoid microwaving food in plastic containers
- Choose glass or stainless steel for food and drinks
- Use protective equipment and good ventilation at work
9. Certain Medications and Medical Treatments
Some prescription drugs can lower sperm count or affect ejaculation. Examples include testosterone, some drugs used for prostate or hair loss (such as finasteride), sulfasalazine for bowel conditions, long term opioid use, and alpha blockers that can cause dry or retrograde ejaculation. Chemotherapy and radiation can also harm sperm. Never stop or change a medication on your own. Ask your doctor whether an alternative is available, and ask about sperm banking before cancer treatment.
10. Untreated Infections and Health Conditions
Several medical issues quietly damage sperm:
- Sexually transmitted infections such as chlamydia and gonorrhea can cause inflammation and scarring in the tubes that carry sperm.
- Mumps after puberty can inflame the testicles.
- Varicocele, an enlargement of veins in the scrotum, is the most common correctable cause of male infertility and is found in about 35 to 40 percent of men with primary infertility.
- Diabetes can lower testosterone and affect sperm and sexual function. Learn more in our guide on how diabetes affects fertility and pregnancy.
- Thyroid and hormone problems can reduce sperm production.
Getting treated early protects your fertility, so do not ignore pain, swelling, or a lump in the testicle area.
What Else Can Affect Sperm Quality?
A few other factors are worth knowing about:
Some lubricants. Many commercial lubricants can reduce sperm movement. If you use one while trying to conceive, choose a product labeled as fertility friendly.
Abstaining for too long. Waiting more than about a week between ejaculations can lead to older sperm with lower motility and more DNA damage. Regular intercourse every one to two days during the fertile window is generally best.
Age. Sperm quality declines gradually with age, and advancing paternal age is linked with longer time to conceive. You cannot change your age, but you can improve the habits above.
Phones and tight underwear. The research is mixed or limited, so there is no need to panic. Focus on the bigger, better proven factors first.
For a broader checklist you can share with your partner, see our guide on what to avoid when trying to conceive.
How Long Does It Take for Sperm to Recover?
Because sperm take about 74 days to develop, most men need around three months of consistent changes before a repeat semen analysis reflects them. Some problems, such as a varicocele or steroid use, may take longer or need medical treatment. Our guide on how long it takes to improve fertility naturally explains the timeline so you know what to expect.
When Should You Get a Semen Analysis?
A semen analysis is a simple, painless test and the best way to find out where you stand. Consider one if:
- You have been trying for 12 months, or 6 months if your partner is 35 or older
- You have a history of testicular injury, undescended testicles, infections, or surgery
- You have erectile dysfunction, ejaculation problems, or low sex drive
- You have used steroids or testosterone therapy
- You have had a pregnancy loss with your partner
Our guides on when to get fertility testing and being not pregnant after 6 months can help you decide, and our full breakdown of male infertility causes, tests, and treatment explains what happens next.
Frequently Asked Questions About Sperm Killers
What is the biggest sperm killer?
There is no single biggest one, because it depends on the person. Smoking, steroid or testosterone use, heavy alcohol, and prolonged heat exposure are among the most clearly documented. A varicocele and untreated infections are the most important medical causes.
Can sperm quality be improved naturally?
Yes, in many cases. Quitting smoking, cutting back on alcohol, avoiding excess heat, improving diet and sleep, and reaching a healthy weight can all improve sperm quality over about three months.
Do tight underwear and laptops really affect sperm?
Laptops resting on the lap can raise scrotal temperature, and prolonged heat can reduce sperm quality. Evidence for tight underwear is weaker, so focus on bigger factors first.
Does masturbation or frequent ejaculation lower sperm count?
Frequent ejaculation can slightly lower the count in a single sample, but it does not reduce your overall fertility. Regular ejaculation every day or two can actually keep sperm fresher and more motile.
Can I take supplements to boost sperm quality?
Some antioxidants, such as vitamin C, vitamin E, zinc, selenium, and coenzyme Q10, have been studied, with mixed results. Talk to your doctor before starting anything, because more is not always better.
Should both partners make changes when trying to conceive?
Yes. Fertility is a team effort, and making changes together is more effective and easier to stick with. It also helps both of you feel less alone in the process.
Take the Next Step
Your lifestyle gives you real influence over your sperm health, and the sooner you start, the sooner those changes show up in your results. If you want personalized support, Katy Poole, a fertility consultant and nurse practitioner, offers one on one fertility consulting services for couples who want a clear plan and answers. You can also explore the Get Pregnant Faster program or browse more fertility health resources.
