In the event that you need any kind of medical care at Heathrow, the airport has the facilities to look after you. There are emergency phones throughout the terminals, a health centre, plus a number of pharmacies.
If emergency medical treatment is required, use one of the internal telephones in the terminal and call 222.
An operator will able to send an ambulance or medical team to the correct location.
Boots chemists are located in all terminals, both before and after passport control. Here you can get medicine over the counter or obtain prescribed medicine, but only in branches before security in Terminal 1 and 5. You can also ask the pharmacy staff for medical advice.