Is there a connection between antibiotics and sperm quality? If you’ve ever needed medicine for strep throat or another infection, you may have wondered whether antibiotics affect your fertility. We’ll take a look at antibiotics’ uses, how they work, and their potential effect on sperm.
What are antibiotics?
Antibiotics are medications that counter bacterial infections. Many antibiotics come as pills, but they can also be ointments, eye drops, or even delivered via injection. A few common antibiotics include:
- Ciprofloxacin (brand names: Cipro, Ciloxan)
- Doxycycline (brand names: Oracea, Monodox)
- Amoxicillin (brand names: Amoxil, Moxatag)
- Metronidazole (brand names: Metrogel, Flagyl)
Why do people use antibiotics?
You may need an antibiotic if you have a bacterial infection that your body can’t take care of on its own. For example, your doctor may prescribe an antibiotic if you have:
- A urinary tract infection (UTI)
- E. coli
- Strep throat
- Whooping cough
Other common bacterial infections, like a sinus or ear infection, may clear up without needing antibiotics, but may require antibiotics if they persist.
Antibiotics don’t work on viruses, so they won’t help if you have a cold, a sore throat, or the flu (your doctor may give you an antiviral instead).
How antibiotics work
Antibiotics work by either killing certain bacteria or making it difficult for them to reproduce. Different types of antibiotics are more effective at treating specific types of infections.
If your doctor prescribes an antibiotic, it’s important to follow their instructions and take the entire course of medication. Doing so helps prevent bacteria from developing antibiotic resistance, in which they stop being restrained by the antibiotic and may cause infections that can’t be effectively treated.
How antibiotics may affect sperm quality and male fertility
Medications may affect fertility by reducing semen volume, altering sexual function, changing hormone levels, or impacting sperm function. Some common antibiotics may affect sperm or even contribute to infertility, according to a 1991 research review. However, research on the impact of antibiotics on sperm is still limited and ongoing.
Animal studies on antibiotics and sperm quality
Many animal studies have suggested that antibiotics have some impact on fertility. In particular, the common antibiotic ciprofloxacin may affect sperm quality. One study from 2012 found that ciprofloxacin was associated with DNA damage in sperm cells and lower fertilization rates in mice. Similarly, another mouse study on ciprofloxacin indicated that this antibiotic lowered serum testosterone levels and disrupted fertility functions even at low doses.
A 2011 study of rat sperm also showed the impact of antibiotics on male fertility, finding that both the antibiotic ceftazidime and the combination of amoxicillin and clavulanic acid lowered sperm motility. The impact was dose dependent, with the highest dose of amoxicillin and clavulanic acid decreasing sperm motility by about 85% and the lowest dose reducing sperm motility by about 49%.
Research suggests that the antibiotics tetracycline and doxycycline may affect sperm in a long-term way, depending on when they are administered. A 2013 study in mice indicated that exposure to these antibiotics during puberty was associated with changes in the testes that negatively affected sperm quality.
Current research doesn’t provide entirely clear answers about antibiotics, though. A study from 2001 found no significant differences in sperm appearance or movement in mice given antibiotics compared to a control group. (It did find that antibiotics induced chromosomal changes, which disappeared gradually over the following weeks.) Research examining the effect of the antibiotic metronidazole on human and rabbit sperm also found that even the highest common doses of metronidazole minimally impacted sperm.
Human studies on antibiotics and sperm quality
In addition to the one human sperm study mentioned above, a few other human studies exploring the influence of antibiotics on human fertility have been done, but overall research is limited.
One research review that focused on male patients with inflammatory bowel disease found that more than half — a much higher percentage than in the general population — had some level of infertility, possibly because of their medications. The review noted that there are few studies on antibiotics, but suggested that treatment with ciprofloxacin or metronidazole could potentially have a negative effect on men’s fertility.
A research review from 2015 came to a similar conclusion. It stated that while there is little research on antibiotics and sperm function, many medications may impact male fertility. As a result, it recommended that men receive counseling about the possible effects of different medications on their fertility.
When antibiotics may improve fertility
Antibiotics aren’t the only concern. It’s important to note that infections themselves, such as STIs, are known to affect sperm health and fertility. Therefore, antibiotics may actually improve semen parameters in some cases by treating infections.
For example, according to research, up to 60% of patients with epididymitis, or inflammation at the back of the testicle, may have decreased sperm development. Inflammation is often a marker of infection. Using antibiotics to clear the infection may return semen parameters to normal.
In another study of 122 men with genitourinary tract infections and reduced fertility, different groups received either an antibiotic (ofloxacin or doxycycline) or no treatment. The study found that men with prostatitis (inflamed prostate gland) and prostatovesiculitis (inflamed prostate and seminal vesicles, the glands that produce semen) who were given antibiotics had greater sperm numbers and a significantly higher pregnancy rate compared to the group that didn’t receive treatment. (On the other hand, there was little change in men who had prostate-vesiculo-epididymitis, despite antibiotic treatment.)
Research from 2003 also supports using antibiotics to improve ejaculate quality in men with pyospermia or leukocytospermia, a condition in which a high number of white blood cells in the semen negatively affect sperm. Pyospermia can be a sign of infection. White blood cells release substances called reactive oxygen species (ROS) in order to destroy organisms that cause infections. But ROS can also affect healthy tissues like sperm, by destroying the sperm membrane, impairing motility, and damaging sperm’s DNA. According to the review of pyospermia patients, antibiotics significantly improved sperm concentration, appearance, and motility in these men.
What should I do if I’m trying to conceive or thinking about testing or freezing my sperm?
While research is ongoing, findings indicate that taking antibiotics or having an infection may each impact fertility. The good news is that the sperm life cycle is about 90 days — so both the impacts of an infection, once treated, or a round of antibiotics should be resolved within a few months.
This is helpful if you are trying to conceive. If you are undergoing fertility treatments or doing sperm testing or sperm freezing, you may want to wait until a few months after your infection has resolved or you’ve completed your course of antibiotics. Taking this extra time, if you can, will help ensure test accuracy and maximum effectiveness of your fertility treatment or your frozen sperm in the future.