Finishers of the London Marathon wear foil blankets

Medical advice

Taking care of your health for the TCS London Marathon

Since 1981, more than one million runners have successfully completed the London Marathon and many more will cross the Finish Line safely in years to come.

Provided you follow these common-sense guidelines, you too should be a picture of health as you cross the Finish Line on Sunday 23 April.

As you know, taking part in these events is beneficial to your health but participants need to take responsibility for their own health by equipping themselves with the right information about such things as training, eating and drinking.

The following simple advice on how to look after your body in the last few weeks building up to event day will help you to have a safe and healthy event.

Medical problems

Discuss any medical problems with your GP. The advice in this document should supplement anything they say.

Fit to compete

Running is good for the heart but even though the risks are small, there have been a very small number of fatalities from serious heart disease in runners apparently unaware that they had a problem. Their condition may have been detected if they had had the relevant heart tests. A ‘fitness test’ is not sufficient to detect these problems.

Please remember, if you have a family history of heart disease or sudden death or a high risk from high cholesterol or high blood pressure, and particularly if you have symptoms of heart disease (such as chest pain or discomfort on exertion, sudden shortness of breath or rapid palpitations), then you should see your GP. They can then arrange for you to have a proper cardiac assessment.

Such an assessment may not be instantly available but continuing to run with these symptoms may be dangerous.


Reduce your training intensity during the last three weeks.

It is much better to get to the Start Line feeling fresh – not exhausted because you have been trying to cram in training that you might have missed.

You should be doing about 80 per cent of your weekly mileage with three weeks to go, 60 per cent of your weekly mileage with two weeks to go and, in the final week leading up to Event Day, your weekly mileage should total about one third of what it normally is.

Illness and training

If you have ‘flu’, a feverish cold or a tummy bug, do not train until you have fully recovered. Then start gently and build up gradually. Do not attempt to catch up on lost mileage after illness or injury – this may cause further damage or illness.

If you have flu, it can take as much as a month to recover. If you cannot run eight miles comfortably one month before the event it is unlikely that you will manage it safely or enjoy it. Please do not run if this is the case. 

If you have had Covid-19, be aware that even mild cases of the disease can result in delayed recovery. Covid-19 can affect almost any organ system in the body. Before getting back into exercise you need to be sure that you have recovered fully, as Covid-19 can cause long term tissue damage which can lead to serious complications during endurance exercise.

Anyone who was hospitalised with Covid-19 has a high risk of cardiac complications due to inflammation of the heart muscle, long term lung changes and/or complications as a result of thromboembolic (clot-related) illness.

Patients who have been admitted with serious Covid-19 should follow the guidance of their health care professionals prior to returning to exercise.

Feeling unwell on the day?

Do not run if you feel unwell or have just been unwell, even if you are raising money for charity.

Most medical emergencies occur in people who have been unwell but do not wish to miss the event. If you feel feverish, have been vomiting, have had severe diarrhoea or any chest pains, or otherwise feel unwell, it is unfair to you, your family and your charity to risk serious illness and become a medical emergency.

You are unlikely to do yourself justice. There will be many other mass participation events.


Drink what you feel you need to quench your thirst. You need to replace some of the fluid you lose as sweat but you do not need to replace it all and you do not need to drink a lot. Drinking too much fluid during (or after) an event can be very dangerous as it can cause hyponatraemia (water intoxication) which can lead to seizures, fits and even death.

THINK before you drink. Individual needs vary with your build, your speed, and, above all, the weather. Using a bottle belt, which is specifically designed to take the 250ml Buxton Natural Mineral Water bottles that will be given out around the course, will enable you to carry a bottle of water with you so that you can drink according to your need throughout the event, using the entire bottle and replenishing with a fresh bottle when required.

You can purchase our specially designed bottle belts online or at the TCS London Marathon Running Show.

Start your run well hydrated and, if you’re not already bursting, drink a small amount of water or sports drink in the half hour before the start.

Slower runners do not need to drink as much as faster runners. If it’s a warm day you may need a little more fluid than usual, but not a lot more. On a cool day all runners should drink less.

Do not drink large amounts of fluid after finishing. You can rehydrate (replace lost fluids) gradually over the next 24 to 48 hours. Try to eat some salty food and stagger your drinks. This way you will not get hyponatraemia and will still replace enough of the water, salt and glycogen lost in running the marathon.

Please don’t take extra bottles of drinking water to pour over yourself as you may be depriving slower runners of their much-needed drinks. If it is hot on race day additional water will be provided and showers will be set up on the course to help runners to cool down. 


Do not change your normal diet drastically in the last week before the event. However, consider eating less protein (meat or plant-based sources such as tofu) and more carbohydrate (pasta, bread, potatoes, cereals, rice), especially over the last three days when you will also be markedly reducing your training (tapering). This helps to load the muscles with glycogen which will delay you ‘hitting the wall’.

Unless you reduce your protein intake, you will not eat enough carbohydrates. (Some runners find it efficient to deplete their carbohydrate levels with a long run on a low carbohydrate diet and then replace it by carb loading, however others find this can make their muscles feel very heavy – so you should not try this for the first time in the week before the event.)

Before your longer runs in the weeks leading up to the event, practise eating your breakfast at the same time that you will eat it on Event Day. You will then be used to eating at the right time for the event.

On Marathon Day

Wear appropriate clothes for the weather when you’re running. On a cold, wet day you can become very cold if you reduce your pace or walk. A hat and gloves will prevent heat loss and are easily carried.

If it is hot, wear loose mesh clothing, start slowly and, if possible, run in the shade. Please don’t wear multiple layers and don’t try to attempt a personal best if the weather is unseasonably warm. Use shoes you know from experience will not give you blisters.

At the Finish

Once you have completed the event, try to keep walking if you can, especially if you feel dizzy. Walking will help to keep pumping the blood back up to the head. Do not stand about getting cold. Get your kitbag and change into warm, dry clothing. Foil blankets will not stop you from becoming cold.

Drink slowly and have something to eat from the recovery items you have packed in your kitbag. Some runners feel faint more than half an hour after finishing a race, often because they have not eaten anything. Again, do not drink excessively.


Large doses of supplementary vitamins and minerals (such as iron) are not essential and produce no benefit if you have a healthy mixed diet, but additional vitamin C in small doses is reasonable if or when fresh fruit and vegetables are in short supply.

Adequate preparation for a marathon requires appropriate nutrition, hydration and rest. Athletes often consume isotonic, carbohydrate and protein drinks as well as energy gels and bars purchased in sports and health-food shops in preparation for the event, which is considered safe practice.

However, over the last two decades there have been an increasing number of commercially available compounds that claim to enhance performance. Some have been found to contain substances banned in other countries and other products (such as steroids) that are banned for use among competitive athletes. Such products are usually purchased via the internet and should not be used by anybody training for a sports event like the TCS London Marathon.

Runners using performance-enhancing compounds that have not been licensed and regulated properly may experience serious side effects and increase their risk of developing heart disturbances that culminate in sudden death. There have been well-publicised cases of runners inadvertently using compounds such as DMAA (an amphetamine-like substance) in an attempt to help them fight fatigue during endurance events and this caused detrimental effects on their health, even resulting in their death.

Do not take unregulated substances bought over the internet.


Topical anti-inflammatory gel or oral painkillers like paracetamol can be helpful if you experience muscular pain during or after the TCS London Marathon. Oral anti-inflammatory medication like ibuprofen, diclofenac or naproxen can cause problems with the kidneys and therefore should be avoided within 48 hours before, during, and after the Marathon. Please note that diclofenac is the active ingredient in Voltarol. Whereas the gel form could be used safely, the oral form must be avoided. 

Professor Sanjay Sharma BSc (Hons), MD, FRCP (UK), FESC, is Professor of Cardiology at St George’s, University of London and the Medical Director of the TCS London Marathon, The Big Half and the Vitality London 10,000. Follow Professor Sharma on Twitter: @SSharmacardio