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Pharmacy and Medications

Oral Contraceptive 21 Tablets vs 28 Tablets



Hi, I wonder what is the benefit of 21-tablet OC and 28-tablet OC. I found 2 types of 28-tablet OC, the one with 7 days inert tablets, which is equal to 21-tablet OC, and the one with 24 tablets active pills and 4 tablets of inert pills. What is the different benefit between taking 21-tablet pill or 28-tablet pill with 7 inert pill and 28-tablet pill with 24 tablets active pill and 4 tablets inert pill?

Can 21-tablet pill or (28-tablet pill with 7 inert pills) be exchanged with 28-tablet pill with 24 tablets active pill and 4 tablets inert pill?


The benefit to taking an oral contraceptive (OC) with 24 active pills, as opposed to the traditional 21 active pills, would be shorter and lighter periods. While taking OC, there is no medically necessary reason for a period. A period only occurs while taking OC when the hormones are withdrawn for that 7 or 4 day time span. If you have fewer hormone-free days, you should experience a shorter and lighter period.

As far as being interchangeable, either type of pill will protect against pregnancy and regulate your menstrual cycle. You could change from one brand of OC to another with little concern about effectiveness. Speak with your healthcare provider about the need for temporary back-up methods of contraception based on your specific prescription and situation.

One area that may vary when switching between brands of OC is side effects. Each type of OC contains a slightly different amount and combination of hormones. While these combinations are all effective, they can produce varying side effects. A three month trial of any OC is usually considered adequate time for your body to adjust and for you to make a decision on whether a pill is right for you. Talk to your healthcare provider about any bothersome side effects you experience to see if adjusting the hormones in your pill may help.

Submitted by:
Jessi Davis
PharmD Candidate 2011
The University of Toledo College of Pharmacy

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Response by:

Carmen M Hadley, RPh, CSPI
Former Clinical Instructor
College of Pharmacy
The Ohio State University