BBB asked
When switching between two combination BC pills do I have to finish the pack before switching? And if I don't finish the pack before switching should I use back up contraceptive?
Answer
Unless your doctor has instructed otherwise, you should generally finish your current pack of birth control pills before starting on a different product.
While all combination birth control pills are similar in that they contain both an estrogen and a progestin, the amount of hormones contained can vary by product as can the specific progestin that is used.
Why Not Switch Mid-Cycle?
Switching mid-cycle to a different pill that contains a different progestin for example, could cause side effects such as spotting, breakthrough bleeding and nausea. Sometimes, even small variations in how you take your pills, like being a few hours late or early in dosing can cause side effects in individuals. Now imagine switching pills mid-cycle and exposing your body to a different amount or type of hormone than it is used to. It makes sense that you could experience some side effects!
Nevertheless, you most likely will still be protected from pregnancy (as you are continually taking active, hormone containing pills) but it is best to start a new pack on a new cycle to allow your body to adjust to the different hormones it is being exposed to.
It is not uncommon for it to take 2-3 months for certain side effects such as spotting go away when starting a new birth control pill product. Switching pills mid-cycle may exacerbate these side effects as well as prolong how long they could potentially last for.
Recommendations For Switching
Lastly, the prescribing information for most birth control pills recommend only to start the product during a new cycle. For example, this is from the prescribing information for Yaz:
"When switching from another birth control pill, YAZ should be started on the same day that a new pack of the previous birth control pills would have been started."
If switching to a continuous birth control pill, like Amethyst, where there are no placebo pills, you should start the new pack on the first day of menses (i.e. first day that you bleed). This means that you will be starting the pills after you have taken all the active pills from your last pack, but presumably before all the placebo pills are gone (if your old pack has them) since menses typically occurs 2-3 days after your last active pill.
If you do switch mid-cycle to a new product, as mentioned above, you should be protected from pregnancy as you are still taking hormone containing pills, which should prevent ovulation. Therefore, there is no need for back-up contraception.
