The Portuguese Health System is universal and based on being resident in Portugal. Expats are entitled to receive state healthcare by registering as a resident and then with their local health centre (centro de saúde).
Portugal has an extensive state health care system, but overcrowding and varying standards of treatment at a local level may make private care a preferred option in some areas, even with the Portuguese. Within the state healthcare system treatment is provided virtually without charge (just a nominal charge) to Portuguese residents. Private medical treatment tends to be expensive, so private medical insurance is advisable if you choose this option. In more rural areas private facilities can also be a long distance away. 
The state heathcare system will not be exactly the same as the NHS in the UK, or your home country, but in many reported cases it is better than the UK. You will have to pay a contribution towards some treatments or services.
Points to Note:
- you will be charged a nominal fee for a state GP consultation (€4,50 in Nov 2016) and hospital consulations (6,50€)
- you will have to pay a contribution towards the cost of any medicines and/or medical exams you may need, such as x-rays, scans, blood tests (e.g. 2€ for ECG)
- spectacles are not available free-of-charge, and can be very expensive in Portugal without any health insurance.
- treatment given privately and repatriation costs to the UK are not covered. Think about whether you want to take out private health insurance
- some social services may not be available
EHIC (European Health Insurance Card)
We have a separate article dealing with this in more detail, called European Health Insurance Cards.
The EHIC is issued by the Social Security depatment of the country you are contributing to and benefiting from.
If you are still a UK resident and only visiting Portugal then you should get a EHIC from the UK NHS. If you are resident in Portugal and pay Social Security then your card will be issued by the depatment of Social Security in Portugal.
The UK - NHS is responsible for issuing the EHIC to UK pensioners resident in other EU countries. For further information on this change visit the NHS website.
Centro de Saúde (Health Centre)
There are variations in these throughout Portugal. But in principle it is your local first stop if you need to see a doctor or nurse. In some area you may not be able to register with a specific doctor, due to lists being full and a shortage of doctors, but you will still be able to see a doctor when you need to.
It would be sensible to register with your local Centro de Saúde as soon as possible, to avoid any unnecessary delays should you need their services. If there is space available you will be registered under a named doctor(your family doctor) if not then you will be registeres but put on a waiting list for a doctor. You can see any doctor at the practive in theory but they much prefer you to see your own doctor.
In some areas there is a main Centro de Saúde in the town or city and subsidiary clinics in some freguesias, which open 1 or 2 days a week. In some towns they have centralised healthcare services into a modern all purpose centre. If you are a long way from a hospital accident & emergency unit then the Centro de Saúde will probably have a SAP or Urgencias clinic which is open longer hours than the doctors surgery, you can go there to see a doctor if you have an urgent need, and cannot wait for an appointment. You will pay a little more for the appointment than you would by making one with your own family doctor, but you would get to see a doctor the same day.
Whatever type of appointment you have with a doctor, if you are in a rural area or a very busy surgery be prepared to wait a long time. Take a book or something to do as you could wait 3-4 hours after your actual appointment time. The level of healthcare in Portugal is very good but the administration systems have a long way to go, and there is a national shortage of doctors. Health Cetres in the cities are much better.
The Pharmácia (Pharmacy) in Portugal
Pharmacies are widely distributed throughout Portugal. They are generally open from 
Monday to Friday, 09:00 am to 1:00 pm, and 3:00 pm to 7:00 pm. On weekends they are open from 09:00 am to 1:00 pm. One pharmacy in each town will be open 24 hours, they work on a rota, the addresses and telephone number is listed on every pharmacy door (look for farmácia de serviço).
Pharmacies in Portugal will often employ 3 or more Pharmacists, they are much more widely used than in the UK, and they can sometimes supply some antibiotics without prescription.
Non prescription medicines like painkillers and cough remedies are not on sale in supermarkets, like the UK, you will have to get all these from the Pharmacy.
Emergencies
The Emergency Telephone Number is 112, for Fire/Amblance/Police. All 112 operators are required to speak some level of English, and some speak other languages too.
This number is common throughout Europe (including UK)