Do antibiotics affect women differently? Doctor explains

You take a pill meant to heal you, but what if your body reacts like it was never fully considered in the equation?

For decades, antibiotics have been developed using data that often leans toward male biology, even though women’s bodies process drugs differently.

The result is a hidden gap in treatment, where the same medicine can work differently, and sometimes less predictably, in women.

HOW WOMEN'S BODY WORKS DIFFERENTLY

The idea lies in a mix of biological and clinical reasons. Women usually have a higher percentage of body fat and lower body water than men, which can affect and change the way antibiotics spread and stay in the body.

Hormones also play a very significant role in changing the way medication reacts in one’s body. Hormones like oestrogen can affect how medication works.

"Women are completely different from men in body size, hormones, metabolism, and function, so they react differently," says Dr. Rishma Dhillon Pai, Consultant Gynaecologist & infertility specialist.

“Their reactions also change during different phases like the menstrual cycle, pregnancy, and menopause. Body changes, such as increased fluid volume and different kidney function, affect how drugs work," she adds.

Our liver is responsible for breaking down medicines, including antibiotics, so they can be removed from the body. However, this process works differently in men and women. Women’s liver generally breaks down drugs slower than men, which leads to the drug staying inside the body longer, increasing the risk of adverse reactions.

In other cases, the drug may be broken down quicker, which can reduce its effectiveness. These variations make it harder to predict the exact impact of the standard dose in women.

WHAT DOES SCIENCE SAY?

The female body is still under-studied in science. Historically, women were often left out of clinical trials due to concerns about pregnancy and hormonal fluctuations.

"Most of the studies are done on men, and women are hardly ever included in trials because researchers are concerned about pregnancy or breastfeeding risks," says Dr. Rishma.

Even today, this gap continues. A 2024 report by the World Health Organization highlights that women are more likely to take antibiotics, often reach higher drug levels at the same dose, and are more prone to infections such as urinary tract infections (UTIs).

Despite these differences, clinical trials still do not fully account for how drugs affect women, raising concerns about safety and effectiveness. Early drug testing also relies heavily on male animals, which means the first data on how drugs behave in the body is often based on male biology.

Even when women are included in studies, results are not always analysed separately. Findings from male-dominated data are often generalised to women, leaving important gaps in understanding.

THE UNEQUAL BURDEN OF SIDE EFFECTS

With antibiotics, women consistently report a higher rate of side effects compared to men. Research suggests women are 50 to 75 percent more likely to experience adverse drug reactions.

Women are also more prone to infections like UTIs, leading to more frequent antibiotic use over time. This increases overall exposure and the risk of side effects.

Dr. Rishma highlights, “In vaginal infections like UTI, when you give them antibiotics, all the bacteria, including the vaginal bacteria die, and they get fungal infections. So this is so common.”

Antibiotics can disturb gut and vaginal microbiomes, leading to issues like digestive discomfort or yeast infections, which are more commonly reported in women. Women also tend to have a more active immune system, which can make drug reactions more intense.

“Because women are not included in trials, there's very little information about how these drugs work in terms of dosage, in terms of frequency of giving the drugs, or how they are metabolising the drugs,” Dr. Rishma points out.

Most antibiotic doses are standardised and often based on male-dominated data. This means the same dose may not suit women’s bodies, leading to over- or under-dosing.

Until medical research fully reflects both male and female biology, this imbalance will continue.

In the case of antibiotics, one size does not fit all. Women’s bodies respond in their own rhythm, shaped by hormones and biology, and recognising these differences is the first step toward safer, more effective treatment for everyone.