The landmark decision should make access easier for people, although buyers will still need to have a consultation with the pharmacist.
The reclassification applies to two brands of “progesterone only” pill – Hana and Lovima.
Combined oestrogen and progesterone pills still require a prescription.
The move has been welcomed by campaigners who say the coronavirus pandemic has made a difficult situation even worse for those trying to access contraception services.
Sexual health doctors say services have been stretched and underfunded for some time.
Hana and Lovima, which contain 75 micrograms of desogestrel, are still available for free on prescription too.
They should be taken once a day, with no break between packs. If a dose is missed by more than 12 hours, the contraceptive effect may fail.
Taken correctly, the mini pill is more than 99% effective, meaning fewer than one in 100 women using it will get pregnant in a year. In reality, because of a range of factors, it is about 91% effective.
Most women can take desogestrel even if they are over 35 and smoke, unlike the combined pill, where risks can outweigh benefits.