They prevent pregnancy by maintaining a constant hormone level which inhibits ovulation.
Pills come in a range of dosages, and a prescription is required for their purchase.
If your prescription is filled through UHS, you will most likely receive a 28-day pill pack. There are several acceptable ways you can start taking your pills, but it's best to follow your health provider's advice. Approach 1 Start on the first Sunday after you begin your period. If your period begins on Sunday, start on that same day. Approach 3 Start on day one of your flow if you are taking Triphasil pills.