How Long After Starting BC Is It Effective (And Why)?

How Long After Starting BC Is It Effective (And Why)?

Exact Answer: 5 days

Are you one of those who intake birth control pills? Then, let me tell you the fact that if you consume it regularly then it assists you in preventing from being pregnant. But in case, you miss out any day then it might be harmful. Well, these pills are quite effective if you consume them properly. In most cases, people do tend to forget to take these pills regularly and they face consequences.

From this, we can say that an ample amount of people do get pregnant every year. For results, you need to be consistent and regular. But there’s no 100% guarantee that you won’t get pregnant if you take birth control pills regularly. There’s a 1% chance that you can get pregnant.

How Long After Starting BC Is It Effective

How Long After Starting BC Is It Effective?

Birth Control PillsConsumption Cycle
Combination pills21 days, 24 days, or 28 days cycle
Progestin-only pills28 days

The duration of birth control pills coming into action totally depends on the time when the pill was consumed. And which type of birth control pill are you using. When you’re thinking of consuming birth control pills then you don’t need to worry. You can consume them anytime any day. But whenever you start make sure you continue it for 7 days.

If you’re taking combination pills that prevent you from ovulating then within 5 days it will work. It would prevent your ovaries from releasing eggs. For example, if you had periods on a Monday morning and then you start consuming pills till Saturday. Then, you’re protected from getting pregnant.

birth control pills

But if you consume progestin-only pills then you’re protected for 48 hours. These pills are responsible for solidifying your cervical mucus and lessens the endometrium. Thus, it prevents eggs from getting fertilized. Slynd which is an exception to progestin-only pills, if it’s consumed on day one then you stay protected right at that moment.

Why Does It Take This Long For BC To Be Effective?

Birth control pills do prevent you from getting pregnant only if you consume them in the right way. These pills don’t work efficiently if you’re suffering from diarrhea or vomiting. Let’s understand how these pills work. First, combination pills operate in two different ways. First, it prevents your body from ovulating. How is this possible? The ovaries don’t allow to free an egg every period. Next, the combination pills harden cervical mucus which is a fluid encompassing your cervix. This fluid aids sperm traveling to your uterus that further fertilizes an egg. Thus, it prevents sperm from entering your uterus.

Progestin-only pills work differently from combination pills. They also thicken cervical mucus but they reduce endometrium too. Do you what is endometrium? It is the covering of a female’s uterus where an egg gets pollinated. If your uterus covering is thin, then it would be difficult to implant an egg. Thus, it prevents you from getting pregnant.

birth control pills

Are you aware of the consumption of these birth control pills? Combination pills come in monthly packages. They have a pattern of 21-day cycles, 24-day cycles, or 28-day cycles. But you can also continue them for 91-day cycles. Make sure you take the combination pills once each day but don’t forget to consume them at the equivalent time of day. Whereas progestin-only pills come with a package of 28 days cycles. Like combination pills, consume one pill every day at the same time.


Do you know what is the reason behind your pill not working effectively? We know that if we have vomiting or diarrhea for about 48 hours then it lowers the effectiveness of the pill. Well, if you consume these medicines then also these pills won’t work. Let’s note down the pills that are antifungal Griseofulvin, antibiotic Rifampin, anti-seizure medicines, and HIV medications.

If everything is out of your reach then make sure you have condoms as a backup. If you’re looking for a longer reason then you need to shift to a separate procedure of birth control. Make sure you consult your doctor before you start consuming birth control pills.


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Hi! I'm Nidhi.

Here at the EHL, it's all about delicious, easy recipes for casual entertaining. So come and join me at the beach, relax and enjoy the food.


  1. Very informative article about birth control pills! I would really recommend everyone to read this article.

  2. I have my contraceptive pills with me, but I didn’t know about these details. Now everything is clear.

  3. I never knew that the effectiveness of birth control pills could be altered if you have diarrhea or vomiting. This article was an eye-opener!

  4. I still have my doubts about the effectiveness of birth control pills, but the article provided a good insight on the matter.

    1. It’s normal to have doubts, but the article provides the information you need to clear them up.

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