Medical Advice

London Marathon Medical Advice

On this page you will find medical information and advice about running the virtual Virgin Money London Marathon from Professor Sanjay Sharma. Please read this advice carefully– we want you to enjoy your big day as safely and comfortably as possible!

It is YOUR responsibility to be fit and well on the day of the marathon in order to enjoy the experience and not put yourself at risk. If you are injured or ill before the marathon you can return your entry for a guaranteed place next year.

Medical problems

Discuss any medical problems with your GP. This advice supplements anything he or she says. See your GP if you have a problem that makes it a risk to run in a marathon. We are happy for people even with serious medical conditions to run, but only with their GP’s and/or specialist’s agreement.


If you have a medical problem that may lead to you having a blackout, such as fits or diabetes, draw a cross on the front of your running number and write the details, especially your medication, on the reverse of the number.

Fit to compete

Running is good for the heart and over the past 35 years, more than one million runners have successfully completed the London Marathon, but there have been several fatalities from serious heart disease in runners apparently unaware that they had a problem. Their condition could have been detected if they had sought medical advice and the relevant heart tests. A ‘fitness test’ is not sufficient to detect these kinds of problems.

If you have a family history of heart disease or sudden death, or have a high risk from high cholesterol or high blood pressure, but particularly if you have symptoms of heart disease; ie chest pain or discomfort on exertion, sudden shortness of breath or rapid palpitations, please see your GP who can 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 shorten your running career catastrophically!


Muscular aches and pains occur most commonly after an increase in training. Training should be increased gradually so that you do not suffer prolonged exhaustion. Separate days of heavy mileage with one or two days of lighter training, or rest days so that your body can refuel your muscles with muscle glycogen are recommended. To reduce injury risk, vary your training runs, the running surface (parkland or hills), the pace and distance and do not always use the same pair of shoes. Always run facing oncoming traffic and be visible; at night wear bright or reflective clothing.

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 as this may cause further damage or illness. If you have flu it can take as much as a month to recover, so consider whether you should run the marathon this time. Note: if you cannot run 15 miles comfortably one month before a marathon, you will not manage it in safety or enjoy it. Please do not run on this occasion.


Fluid lost in sweat must be replaced otherwise your body becomes dehydrated (short of water) and less efficient. Alcoholic drinks, tea and coffee are dehydrating. Take plenty of non-alcoholic drinks, especially if you’re training in hot weather. Drink enough to keep your urine a pale straw colour. Drink plenty of liquids after training, especially long runs, and practise drinking during longer training runs. Try Lucozade Sport in training to see if you like it.

Drinking on the run needs practice. Drink plenty of fluids but preferably no alcohol in the two days leading up to the virtual Virgin Money London Marathon. Do not drink excessively just before the event, during the run or gulp water after wards as you may get hyponatraemia (see below).

Drinking on the day

Start the challenge well hydrated and if you are not already bursting, drink half a pint (250ml) of water or sports drink in the half hour before you start.

Drinking safely

Drinking too little can lead to problems, as you need to replace some of the fluid you lose as sweat. Drinking too much can also be very dangerous and lead to hyponatraemia (water intoxication), fits and even death. Drink only when you feel the need and do not gulp large volumes of fluids before, during or after the event.

Your needs vary with your build, your speed and above all the weather. Faster runners (under 3:30) on a warm day may need as much as a litre of fluid per hour (around two pints). Slower runners should need to drink less, particularly on a cool day, and should not drink more than 500ml (around one pint) of fluid per hour.

After you’ve finished, do not drink large amounts of water. It can be quite normal to not pass urine for several hours after a marathon. You can only rehydrate (replace lost fluids) gradually over the next 24 to 48 hours. Try to eat some salty food as well as spacing out your drinks. This way you will not get hyponatraemia and will still replace the water, salt and glycogen lost in running the marathon.


Large doses of supplementary vitamins and minerals (such as iron) are not essential and produce no benefit if you are on a good mixed diet, but taking additional vitamin C in small doses is reasonable when fresh fruit and vegetables are in short supply. Training (with adequate rest) helps you to sustain a high level of muscle glycogen if you eat enough carbohydrate. If you can, eat within two hours of your long runs. This helps to rapidly replace the muscle glycogen and hastens recovery.

Do not change your normal diet drastically in the last week before a marathon, but eat less protein (meat) and eat more carbohydrate (pasta, bread, potatoes, cereals, rice and sweet things), especially for the last three days when you should also be markedly reducing your training. This loads the muscles with glycogen and delays or prevents you ‘hitting the wall’. Unless you reduce your protein intake you will not be able to eat enough carbohydrate. Not all runners are helped by first depleting carbohydrate levels with a long run and low carb diet and then loading as this can make your muscles feel very heavy.

Still fit?

Do not run the marathon 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 sponsoring charity to risk serious illness and become a medical emergency. You are unlikely to do yourself justice. There are many other marathons.

On the day

Wear appropriate clothes for the weather. On a cold, wet day you can become very cold if you reduce your running 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. Use shoes you know from experience will not give you blisters.

At the finish

Once you have completed the challenge, do not stand about getting cold. Make sure to keep walking, especially if you feel dizzy, and gradually drink enough fluid to replace lost liquid. Change into warm, dry clothing. Keep on drinking slowly and have something to eat. Some runners feel faint more than half an hour after finishing a marathon, often because they have taken insufficient fluid and/or not eaten anything. Again, do not drink excessively.

Think before you drink

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 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 in an attempt to help them fight fatigue during endurance events and this caused detrimental effects on their health, resulting in their death. In one recent case toxicology identified traces of DMAA, which is an amphetamine-like substance. Although banned in sport, the product was legally available at the time and advertised as a powerful performance enhancing agent and the warnings associated with the potential harmful ingredients were not highlighted on the product. Runners should avoid consuming unregulated substances bought online.

Preventing hyponatraemia

The 2007 London Marathon was the hottest in the event’s history and was sadly noteworthy for the death of 22-year-old David Rogers from hyponatraemia – a condition which can be caused by overhydration. There were 12 other cases of hyponatraemia the year before, six of whom required emergency treatment in hospital. Again, it is likely that all of these runners drank more than necessary for the hot conditions, despite the official advice given by the London Marathon on safe drinking during the race. The 1996 London Marathon was run on a similarly hot day and while there were complaints about the water running out, we had no significant cases of hyponatraemia that day.

In 2003 there were plenty of drinks available for what was another warm marathon day, but on this occasion we had 15 hospital cases of hyponatraemia. Many runners are drinking too much! THINK before you DRINK.