There isn't a general legal requirement for your employer to give time off for medical appointments. Whatever entitlement you have to time off to visit the doctor will be governed by your individual employment contract.
You should check your contract and staff handbook, as this may specify what the regulations are in your workplace. Some employers may require you to take annual leave or take the time unpaid. On the other hand, many employers will be flexible on this and it may be worth asking your employer if you can make up the time later.
If you have a disability which requires you to make regular medical visits, there is a law prohibiting disability discrimination. Under the Equality Act 2010, your employer must make 'reasonable adjustments' to prevent you suffering a disadvantage compared with non-disabled workers. Reasonable adjustments could include greater flexibility in your hours, or availability of time off (paid or unpaid) when you need it. Everybody’s case is different, so it would be a good idea to seek individual legal advice from your union or solicitor.
See our Dealing with Doctors section for more information.