...to stop their "irregular" periods or whatever they want to achieve?
Crikey OCP's as they are called are usually prescribed for different reasons other than the primary one being contraception . Irregular cycles is one of those reasons but it is advisable to take them only after a doctor's consultation to rule out other causes of irregular cycles.
There are different factors taken into account , including age , weight , history of thromboembolic disease , hypertension ,cancers etc before we prescribe OCP to a patient .
If you have any queries feel free to ask !