Patients in Wales are now entitled to free prescriptions, as the cost rises to £6.85 in the rest of the UK.
Some patients in Wales already qualify for free prescriptions
Prescription charges had been gradually reduced to £3 - but Welsh assembly members voted earlier this year to scrap them altogether from 1 April.
GP and pharmacist representatives in Wales said scrapping the charges was "good news" for those who find paying for medicines difficult.
However, manufacturers have warned it could lead to drugs going to waste.
Prescription charges are rising by 20p in England, Scotland and Northern Ireland.
Last year the price of prescriptions in Wales dropped from £4 to £3.
The aim of the policy is to reduce patient inequality and it is expected to cost £29.5m in the first year.
Dr Andrew Dearden, chairman of the BMA's general practitioners committee in Wales, said: "The introduction of free prescriptions in Wales is good news for those who find paying for their vital medications difficult.
"Evidence shows that some patients do not take their medicines due to not being able to afford all those prescribed by their GPs.
"This should aid people in taking their medications as advised, free of the worry of payment."
PRESCRIPTION FACT FILE
The price of prescriptions was frozen at £6 in Wales in 2001, then reduced to £5 in 2004, £4 in 2005 and £3 in 2006.
Previously prescriptions were free to those under 25 and over 60 or who had certain medical conditions or low income.
Over-the-counter drugs, which do need a prescription, are not included.
GPs will continue to assess if patients should have medicines on prescription.
The 3m patients registered with a Welsh GP or 15,000 Welsh patients with an English GP and an entitlement card will qualify.
But Anglesey GP Dr Catrin Ellis Williams said: "I don't think necessarily it will good idea for everybody because there are many people who are perfectly able to pay the £3 prescription fee as it is.
"We hope it doesn't change people's attitudes towards the service and people won't be phoning their doctor for a simple medication which is accessible over the counter."
The scrapping of charges was welcomed by patient organisations.
Peter Johnson, director of Arthritis Care Cymru, said: "Having this scheme available to Welsh arthritis sufferers will benefit them enormously, lessening the financial strain for them."
Trish Hughes, general manager for Wales at the Stroke Association, said: "This will be a great relief to many stroke sufferers in Wales. We wholeheartedly support this measure."
The scrapping of the charge will apply to just over 3m patients registered with a Welsh GP and those 15,000 Welsh patients who have an English GP, who with an entitlement card will be able to get free prescriptions from a Welsh pharmacist.
The Association of the British Pharmaceutical Industry has already warned that free prescriptions could lead to demand for medicines increasing and pressure on the medicines budget.
But Steve Symonds, a Swansea-based representative of the National Pharmacy Association, said he believed reductions in prescription charges since 2001 had not resulted in greater demand and would bring a number of positive aspects for pharmacists.
He said it would mean an end to difficult decisions at the counter facing some patients, who would drop items off their prescriptions to save money.
Mr Symonds said: "The system is very inequitable.
"You may have a lady in her mid 20s earning just above the minimum wage who will have to pay for prescriptions and she may be living next to a multi-millionaire, who has prescriptions free simply because he is over 60."
Former health minister Edwina Currie, now a trustee of the Patients Association, said the move undermined the idea of a single NHS.
She added: "It seems quite bizarre that on opposite side of the Severn Bridge we're going to have completely different rules, and it is certainly going to make patients on the English side feel really quite hard done by."