Getting your period on race day, or in the middle of a big training block, is not a rare event. It's a reality for millions of female athletes. Yet it's still rarely talked about openly in running.
In 2015, Kiran Gandhi ran the London Marathon on her period without a tampon, and the image of her crossing the finish line sparked a global conversation about periods and stigma. Since then, more and more athletes have spoken openly about training and racing through their cycle.
Here's what every runner, and every coach, should know.
Your cycle in a nutshell
A typical menstrual cycle lasts around 28 days, but anywhere from about 21 to 35 days is common. It's usually described in two main phases:
- Follicular phase : from the first day of your period until ovulation: estrogen rises, and many athletes report feeling stronger and more energetic in the days after their period ends.
- Luteal phase : from ovulation until your next period: progesterone rises, body temperature increases slightly, and some athletes feel heavier, more tired or less tolerant of heat.
Does your period affect performance?
The honest answer: it depends on the runner. Research on the menstrual cycle and performance has produced mixed results, and reviews suggest that any average effect is small and varies a lot between individuals. Some runners set PRs on the first day of their period. Others feel flat for a few days.
What's more consistent is the impact of symptoms. Cramps, bloating, fatigue, poor sleep and digestive issues can all make a run feel harder.
Practical tips for running on your period
- Track your cycle alongside your training. After two or three months, patterns often appear. You may notice when hard sessions feel best and when to plan easier days.
- Don't skip the run by default. Light to moderate exercise can ease cramps and lift mood for some people. Listen to your body and adjust.
- Test your products in training. For long runs and races, many runners prefer menstrual cups, period underwear or a tampon changed right before the start. Find what works on long runs, never on race day.
- Wear darker shorts if it helps you feel comfortable. And remember: nobody at mile 20 is judging you.
- Fuel and hydrate well. Iron needs are higher for menstruating athletes. If you feel unusually tired or short of breath, ask your doctor about checking your iron levels.
- Be careful with painkillers. Talk to a healthcare professional before taking anti-inflammatories around long efforts, as combined with dehydration they can put stress on the kidneys.
When to see a doctor
Missing periods are not a badge of honor. If your periods stop or become irregular while you're training, it can be a sign of low energy availability, often linked to under-fueling. This condition, known as RED-S (relative energy deficiency in sport), affects both bone health and performance. Very heavy or very painful periods are also worth discussing with a professional.
The bottom line
Every athlete experiences their cycle differently. Some slow down, others race as usual. Both are valid. The most important thing is to know your body, plan around it when you can, and never treat a normal part of life as something to hide.
