Hello and welcome to our live page covering the industrial action being taken by doctors across the UK. The extent of disruption today is not yet clear. The NHS is advising patients who need help in an emergency to use the service as they normally would. We'll bring you all the news and analysis from the day as it unfolds.
Appointments for urgent tests, such as for cancer, are expected to go ahead as planned. Accident and emergency units will remain open, while mothers in labour will be able to go to maternity departments. But routine appointments and operations could be affected, the BMA has warned.
BBC correspondent Dominic Hughes is at Barnsley Hospital, where he says they've had to cancel or postpone eight operations out of 52. The hospital has also postponed around 20% of outpatient appointments. The medical director says the industrial action should have a fairly low impact on patients.
Dr Prit Bittar, a GP in his 50s and a former member of the BMA's General Practitioners Committee, tells BBC Radio Berkshire that he's striking "with great reluctance... we've been driven to this by a government which has refused to negotiate with us".
Doctor Paul Cundy, a GP who has a surgery in Wimbledon, told the Today programme earlier that he is taking industrial action "very reluctantly". He said he "understands that patients feel they are caught in the middle of this".
BBC health correspondent Nick Triggle says: "The scale of the disruption to patients will depend on just how militant doctors are. Ahead of the day of action, plenty of doctors said they would be supporting it but would not be turning patients away even for routine appointments. This has meant that some NHS trusts have cancelled only a very small proportion of bookings in advance."
Our correspondents across the UK will be aiming to help us build up a picture during the day of how much affect the industrial action has been having. BBC Radio Oxford is first off the mark with some figures outlining the situation around its region. In Oxfordshire itself, 29 GP practices are taking action, 49 are not and six did not reply.
In Buckinghamshire, nine are, 48 are not, in Wiltshire the split is 20/38 and in Swindon we've learned that 27 are taking action but have yet to get a definitive figure on how many are not.
Trevor Pickersgill, a consultant neurologist at the University Hospital of Wales in Cardiff, tells BBC News viewers that doctors are sorry for any inconvenience. "Patients are still our first priority," he says, but explains that this is the first time in nearly 40 years that doctors have felt this strongly about changes to their pay and conditions. There have been cancellations for elective surgery such as knee and hip replacements at the university hospital and Dr Pickersgill warns this could be the "first day" of further industrial action.
So do you understand what today's action is about? Doctors are angry that the government is changing their pension scheme just four years after a new deal was reached - but the government, in turn, insists it is not sustainable. The British Medical Association - the doctors' trade union - has argued that contributions are going up too much and that asking doctors to work until they are 68 is wrong and could harm patient care. Our Q&A explains the issues on both sides.
The last time doctors took industrial action was in the mid 1970s when consultants and junior doctors decided to withdraw non-emergency services, the BBC's Neil Bowdler writes. The consultants worked to rule and suspended all "goodwill activities" between January and April of 1975 in protest against proposed new contracts which they said would force them to abandon private practice.