Medical Instructions for Marathon Runners


The intention of this advice section is to help you prepare for a successful day and a performance you can look back on with pride. The advice is given in good faith to help you enjoy the day.   This information has been put together by Dr Aisling Diamond (Official Belfast City Marathon Doctor).

Whether you are running, jogging or walking one of our events, it places huge stresses on the cardiovascular, musculoskeletal and heat regulating systems. Energy demands can be increased by a factor of 10-15 fold.  Successful participation requires adequate acclimatisation and training as well as fluid and fuel intake.

If you have any medical problems that you fear may interfere with your training programme, or make it risky to take part in the Marathon / Half Marathon then discuss them with your GP. This advice section supplements anything he or she may say. Please ensure you notify the Official Marathon Doctor at of any pre-existing illness in advance of Race Day. This information is confidential and will ONLY be reviewed by the doctor.

1. Training.

Remember the principle of training is to gradually increase the intensity and duration making sure that you have a recovery or rest time in order for the body to recover.


- Increase training gradually so that you do not suffer excessive fatigue; make sure you build in rest days and try and not have a sudden increase in intensity or duration of your runs.

- If you have flu, a fever, or a tummy bug, avoid training until fully recovered. Training or racing while you have a temperature or the flu can put you at risk from heart inflammation which may be irreversible. Rest until you are better then start at a lower mileage and intensity and build up gradually. It can be counterproductive to try and catch up on lost mileage because it may cause further problems.

- To reduce risk of injury train on soft flat surfaces whenever you can parklands, footpaths, fields.

- Injury. Do not attempt to train if you are carrying an injury. Seek advice from your GP. Replace running with biking or swimming if possible while you recover.

- If you cannot run 15 miles comfortably before a full marathon you may not be fit enough to enjoy or manage the distance in safety.


2. Diet.

- 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. The addition of a supplement has been linked to the death of Claire Squires in the London Marathon. At the time of her death this supplement was legal.

3. Fluids.

- The recommendations on fluid replacement have changed considerably over the last few years. Although you need to replace fluids lost in sweat there is a danger of drinking too much fluids which may reduce your blood sodium levels and make you unwell. This problem is more likely to occur if you are running for more than 4 hours, take on more fluid than you lose, or if you are taking non steroidal anti-inflammatory tablets (if you require anti-inflammatory medication you should consider withdrawal). 

- Try and train to drink while you run. There is emerging evidence that cold drinks after exercise may be associated with the development of abnormal heart rhythms. Please desist from drinking cold drinks before, during or after the marathon. 

- The sports drinks with carbohydrate concentrations are designed to provide calories in a form that can be absorbed with a decent proportion of fluid. You will need to experiment to find one that suits you.

- Alcohol is dehydrating. A pint of beer produces more than a pint of urine and spirits have an even worse effect. Drink non-alcoholic drinks before you train and immediately afterwards.

- Weighing yourself before and after your training runs will give you some idea of your fluid losses; hotter conditions will mean higher fluid loss and cooler conditions lower fluid loss.

4. Clothing. 

- Wear comfortable clothing. Trendy clothing with sewn-on trimmings can rub your groin and nipples until they bleed. Wear kit that is comfortable. Don’t wear it from new - wear it and/ or wash it before you run in it .Vaseline applied to these areas can protect the skin.

- Find shoes that are comfortable over long distances. Remember the shock absorbency of your shoes will diminish as they get older. Wear the right shoes for you. Go to a reputable sportswear store and seek advice. Take along your old trainers for inspection. By the time of the marathon you will have a pair that are comfortable and not worn out.

-Please ensure the skin on your feet has hardened up before Race Day.


5. On the day.

- Do not participate if you feel unwell, have a fever, have had diarrhoea, vomiting or chest pain within the previous 72 hrs. You will certainly not perform well and you will put yourself and your future running at risk. Remember running with fever can cause serious complications. You can defer your entry for the Deep RiverRock Belfast City Marathon or Half Marathon events (to the next year) with a medical note from your GP. 

- If you have a medical problem which may lead to an emergency, such as fits, diabetes, asthma or if you are on any medication e.g. blood pressure tablets write details on the reverse of your number.  Please email details before the race.

- Wear appropriate clothing for the weather. On a cold, wet day you can become very cold if you slow down or walk; a hat and gloves prevent heat loss and can be carried if not worn.

- If it is hot wear loose mesh clothing, start slowly, and pick out the shade on the course.

6. At the Finish.

- Do not stand about: This will certainly make your blood pressure go low and you are likely to faint. Keep walking or sit down for a few minutes. You will tend to get cold once your muscles stop working so once finished, go to the Bag Collection Area or wherever your clothes are stored and change into warm, dry clothing. Foil blankets do not stop you from getting cold.

- Drink as soon as you can because your body will be short of water and sugar; sports drinks, cereal bars, or your favourite post training snack. 

- If you feel faint lie down.


7. Medical Aid.

- Train sensibly and follow this simple advice and you will have done a lot to avoid the need for medical aid.

- If you drop out make for a first aid point where you will be ferried back to the finish. There are medical teams placed throughout the Marathon / Half Marathon, please see the relevant maps provided within each events section.


Conditions Associated with Marathon Running.

1 . Exertional Hyponatraemia (Water Intoxication)

This presents several hours after the start of the race as a result of excessive fluid intake with headache, mental confusion and often vomiting and in severe cases, epileptic seizures. It can be a problem with non-elite runners drinking too much fluid before, during and after the race. Please ensure you train using the fluid you will drink during the marathon.

2.  Hypothermia and Hyperthermia

See above

3.  Cardiac Arrest

This occurs in 1:50,000 runners. The runners are normally affected in the later stages of the marathon.

The commonest cause is coronary artery disease. This affects the arteries supplying the heart muscle. If you have a family history of angina or heart attacks please consult your GP before running.

Cardiac arrest can occur in young runners. The cause is usually a condition which affects the heart such as HOCM or congenital problems. Please consult the cardiac specialist who manages your condition before running and ensure you email details to the organisers of the Marathon.

If you experience chest pain in the weeks before the race please consult your GP. Please do not ignore this. One of the younger runners who suffered a cardiac arrest in South Africa had experienced chest pain in the week prior to the Marathon.

If you experience chest pain while running please stop and notify the first aid team. There are numerous teams situated throughout the course of the Marathon.


If you experience ANY of the following symptoms, please do not attempt to take part on race day:


❗️Viral illnesses eg diarrhoea, cough, cold, sore throat over the last month




❗️Chest discomfort


❗️Chest pain


❗️Palpatations or breathlessness


❗️General feeling of being unwell


❗️Any changes in your normal medication


❗️Injury in last month


Important information for those impacted by the following conditions:

  1. Any runners who have Anaphylaxis must carry 2 epipens while participating in the half marathon / marathon.  Those with anaphylaxis to food should be aware their are food stalls at the finish area
  2. Any runners who have Asthma should carry their inhaler at all times
  3. Any runners who have Diabetes should run with their BM monitor and glucose replacement.  If using the event High 5 Energy Gels or PowerAde from the energy points along the route - please ensure you have used the brand during pre-event training
  4. Any runners who have Epilepsy should take their medication and have discussed this Half Marathon / marathon with their doctor

  5. Any runners with heart conditions should discuss participating in this Half Marathon / marathon with their doctor and/or cardiologist


If you have any questions, please get in touch with Dr Aisling Diamond (Official Belfast City Marathon Doctor) at