Blisters, sore muscles and what seems to be a never ending training schedule are just some of the effects of preparing for a marathon.

On Sunday, 2 October, 50,000 people will be putting on their running shoes to take part in the London Marathon. An event like no other, it’s a chance for runners to celebrate after months of training and fundraising, while being cheered on by friends, family and complete strangers. It is easy to see why it’s a challenge many runners dream of completing.

However, for many of those taking to the road, there’s been another obstacle to get over, one that’s not always talked about – their period.

Stomach cramps, insomnia and leaking are just some issues runners have to manage while on their period – issues that could affect their performance in the marathon itself.

Alana, a runner from Surrey, says her period has negatively impacted her training. “I’ve missed runs because I’ve suffered so badly with insomnia and a lack of energy due to my period,” she says.

“This then leads to being anxious. Recently I missed a 20-mile run because I got my period and I’m now worried if I’m even going to be able to do it anymore.”

It’s a concern of professional runners too.

Paula Radcliffe revealed she was suffering with period-induced cramps during the last third of her then world-record-breaking Chicago Marathon victory in 2002.

During the 2022 European Championships in Munich, high-profile British athletes Dina Asher-Smith and Eilish McColgan spoke about how their periods had negatively affected them during competitions.

“My menstrual cycle has always affected my training in some way,” McColgan told BBC Sport. “My legs usually feel very heavy and flat. Normally I’ll have bad stomach cramps, bloating and a sore lower back.”

McColgan is among a number of professional athletes to have called for more guidance and support on the matter.

“There’s no information on it at all,” says Alana. “We get sent through so much information about managing your wellbeing alongside your training, but there’s nothing to say how to manage the menstrual cycle with that.

“I’m likely to be on my period for marathon day, so then come the questions: how is that going to look and what can I do?”

Professor Kirsty Elliott-Sale, a professor of female endocrinology and exercise physiology at Manchester Metropolitan University, admits there is limited information on managing menstruation and sport.

“A lot of research in this area is moderate, low and very low in quality,” she says. “That is because female physiology and female endocrinology [hormones] is not taught as part of the sports science curriculum.

“So if you do a sports science degree, in your three years you just really hear about male physiology and male biomechanics.”

Another reason for the gap in research is that periods affect women differently.

“You’ve got world records set [by women on their period] when other women can’t get out of bed with bad cramps,” she adds.

Dr Juliet McGrattan, a women’s health expert and author of Run Well, wants to reassure runners they can train and perform well during their period.

“Science hasn’t given us all the clear recommendations that will suit everybody,” she says. “But the best way is to track your cycle, either with an app or just with a pen and paper, and see what the patterns are for you.

“There might be times of the month when you feel like you’re better with those intense training sessions, like interval runs or hill runs, and times when you find that your longer, endurance runs are easier.

“The best way really is to just see what works for you, and be flexible and adapt to try and work with your body rather fighting against it.”

Managing the pain with paracetamol could help, while exercise has been shown to ease symptoms for some. A Cochrane review in 2019 found exercising 45-60 minutes three times a week at any intensity reduced menstrual pain significantly.

Dr McGrattan also suggests seeking advice from your GP about ways to delay your period, for example by taking the combined pill without a break.

For those who are menstruating on race day, there are practicalities to consider too.

For Alana it has become an added worry: “I’ve got to think about whether I need to carry any sanitary products with me, and I need to buy darker shorts.”

Lauren Thomas, who is behind the blog Girl Running Late, would like to see better facilities at events. “I just don’t think race organisers think about whether or not portable toilets are OK. From a hygienic perspective, races aren’t great,” she says.

“Races are not organised with periods in mind. I would love to see that change.

At the 2015 London Marathon, Kiran Gandhi, author of the blog Madame Gandhi, ran the 26.2 miles without using any sanitary products to raise awareness of the issue.

London Marathon organisers said: “We currently provide free menstrual products for participants in need of them at the information points on each of the three start areas, and menstrual product bins are placed in toilets.”

They also said they were “developing a range of new training advice materials for all our events in 2023 [running, cycling and swimming] and this will include expert guidance for women on how best to manage their periods during training and on event days”.

One of the best ways to make change is by speaking about it. As Thomas says, “The more people talk about it with their running buddies, the better it will be.”