Pharmacists will be able to issue repeat prescriptions without the need for a GP under a new contract which comes into force on Friday.
Patients will be able to get repeat prescriptions without seeing a doctor
The new rules will also allow some pharmacies in England and Wales to review patients' treatment for long-term illnesses such as diabetes.
The government says it is an important step towards modernising the service.
But GPs fear it may reduce the quality of information available to vulnerable people.
The framework was drawn up after two years of talks between the Department of Health and pharmacists' representatives.
Ninety-two per cent of pharmacies voted in favour of the contract.
The contract says all pharmacies should provide repeat prescriptions, health advice and the disposal of unwanted medicines.
A GP will be able to give a prescription lasting up to a year, allowing the patient to get their medicine from the chemist as and when they need it.
Pharmacies have until October this year to introduce the changes.
Many will also offer extra services like diabetes care and stop-smoking clinics.
Some may also choose to offer drug reviews for people with long-term conditions such as asthma and diabetes.
Health Secretary John Reid says the contract will make better use of pharmacists' expertise.
Pharmacists will offer advice on long-term conditions
"As well as giving you your medicines, your pharmacist can now also give you lifestyle advice on how to become healthier.
"This will help to tackle national diseases such as obesity and cancer, and they will take part in local and national health promotion campaigns".
President of the Royal Pharmaceutical Society of Britain, Nicholas Wood, said: "The contract opens the door on a wide range of new services to meet the needs of real patients".
But Dr Graham Archard, vice-chair of the Royal College of General Practitioners, warned: "While pharmacists do a good job they are not trained to carry out the same specialist health care roles as GPs.
Pharmacies - key facts
1.8 million visits to pharmacies each day
There are 10,000 community pharmacies in England
Each adult visits a pharmacy 12 times a year on average
"There are possible negative effects of fragmentation in primary care - something we have been warning against for some time now - and it is important that the GP's role is not eroded."
The government has also published revised rules allowing pharmacies to be located in large shopping centres away from town centres, or for more than 100 hours a week.
Licences will also be available for the first time to those opening internet-only and mail order pharmacies.
The Department of Health has said there will be strict rules to ensure that these pharmacies provide a professional service.