Exactly How The Pill Changes Your Cycle

We at Bustle love giving you tips for how to tap into your sexual potential and troubleshoot when things aren’t going your way in the bedroom. But what about finding solutions to those stressful sexual health situations that inevitably crop up when you’re getting down? Emma Kaywin, a Brooklyn-based sexual health writer and activist, is here to calm your nerves and answer your questions. This week’s topic: Your menstrual cycle on hormonal birth control.

Q: I’ve been on the pill for 10 years. My doctor put me on it in high school before I was even sexually active, to help me manage super painful cramps. And it totally worked for that! Recently though, I’ve been thinking that I actually don’t know much about how hormonal birth control is impacting my natural cycle or even if I really have one anymore. I’ve heard that it makes people’s periods lighter, and I’ve noticed that I have fewer PMS symptoms than many of my lady friends overall. So my question is: How is my cycle different because I’m on the pill? Am I still getting a “real” period?

A: Hormones are powerful. Just a small fluctuation in your hormone levels can have profound effects, from changing your metabolism to dictating if you wanna get down and dirty or curl up into a ball and sob for days. So it’s no surprise that introducing synthetic hormones into your body — which is what you do when you take hormonal birth control like the pill, the ring, or the shot — affects you on a number of levels.

A note on periods and gender identity: It’s worth articulating that not everyone who identifies as a woman has a menstrual cycle, and not everyone who has a menstrual cycle identifies as a woman. I will be using gender-neutral language throughout this piece to reflect this richness of life experience.

Hormonal Birth Control 101

First of all, how does hormonal birth control work? When you’re on your natural menstrual cycle, your hormone levels are dipping and rising all the time in a bunch of what we can call mini cycles. The main players involved are estrogen, progesterone, and testosterone. The presence in varying levels of these three hormones in your body trigger different parts of your cycle — such as thickening your endometrium (the nutrient-rich lining of your uterus that grows to feed any hypothetical embryos), maturing your eggs, and releasing them into your fallopian tubes so they can canoodle with any sperm that may be hanging around.

Hormonal birth control changes the levels of these hormones in your body by introducing synthetic hormones. Some oral contraceptives have a mix of estrogen and progestin (the name for the synthetic progesterone look-alike), and others have just progestin. Since these hormones are the key orchestrators of your menstrual cycle, it makes sense that your menstruation and ovulation would be different as a result of taking hormonal birth control. Let’s learn about it!


Ovulation is when your ovaries release a mature egg, aka one that’s ready to be fertilized. Once set free, the egg travels through your fallopian tubes, where it can encounter any sperm hanging around, resulting in the very early beginnings of a human child. Ovulation is triggered by very low levels of estrogen, testosterone, and progesterone.

How It's Different On The Pill

When you’re on the pill, you can’t have low estrogen or progesterone at this point in your cycle because you’re actively taking synthetic versions that are keeping your levels high. So in essence, the pill stops ovulation because the levels of estrogen and progesterone you’re taking don’t allow the hormone dip that triggers your natural monthly egg maturation and drop.

Wait, but then how can you still get pregnant if you're on the pill? Great question! Oral hormonal birth control isn't 100 percent effective — after all, no birth control method (other than abstaining from sex, which isn't really a form of control so much as just opting out altogether) is. If you take your pill correctly — so, every day — it's been shown to be 99.9 percent effective in stopping pregnancy, which is pretty much as good as it gets. However, you can get pregnant right after you stop taking the pill, because your body is resilient and reverts back to its natural hormone levels very quickly. If you skip even one dose, there's a chance of pregnancy.


Your body gets ready for menstruation during the luteal phase of your cycle, which starts the day after you ovulate and ends when your period starts. In this phase, your body starts creating high levels of progesterone and estrogen, which cause your uterine lining to thicken to get ready for a potential embryo.

Menstruation is triggered by a drop in estrogen, testosterone, and progestin, which occurs if your uterus doesn’t receive an embryo after ovulation. This drop also triggers premenstrual syndrome aka PMS, which can be extremely unpleasant for your body (think cramps, bloating, breast tenderness, lethargy, headache or migraine, acne flare-ups, diarrhea, constipation, insomnia, and food cravings) and mood (anger, irritability, depression, oversensitivity, anxiety, self-hatred, nervousness, and crying, often with rapidfire switches between these emotions).

How It's Different On The Pill

As with ovulation, the hormonal changes that trigger the thickening and subsequent breaking down of your endometrium don’t occur if you’re taking daily hormones, so you don’t get your period. The lack of a hormone drop also results in a lack of PMS, which is why so many people take hormonal birth control to combat the physical and emotional side effects of their cycles.

However, many oral birth control options do give you a semblance of a period — it happens when you take that week of sugar pills that come in your monthly packet. A great deal of research has shown that you don’t actually need to bleed each month, which is why some people choose to skip the placebo week and just keep on keeping on with the hormone pills.

In fact, the reason the sugar pills exist is historical — back when the pill was first put on the market in 1960, the creators thought that preserving the appearance of a menstrual cycle would make the product more marketable to its users, who wouldn’t necessarily have to disclose that they were on it to their partners (or church, which was and still is very uneasy about birth control, to put it in the most gentle way possible).

So What Is That Monthly Bleeding, If It’s Not Your Period?

It’s called withdrawal bleeding, and it’s your body’s reaction to going into withdrawal from the levels of hormones to which it has become accustomed during the rest of the month. Withdrawal bleeding is often shorter and lighter than your natural period, because the hormonal birth control has suppressed your endometrium from thickening (since you aren’t ovulating so you can’t get pregnant and your uterus won’t be needing to feed a tiny human), so there literally isn’t much to shed.

The Bottom Line

Hormonal birth control definitely changes your body a lot. It can alter your weight, your skin, how you experience PMS, and as we’ve just learned, the inner workings of your reproductive cycle. For most people, this isn’t a problem — the pill has been in use since 1960, which means there’s a ton of research on how synthetic hormones interact with your body. Significant research shows that the pill is not only useful, but by and large very safe. And for some, it’s spectacular and solves all their problems — kinda like a magic bullet, but for your ladyparts. So if you’re taking hormonal birth control and loving it, rejoice! You have found a method of birth control that works for you.

If, however, the thought of messing so profoundly with your menstrual cycle freaks you out, that’s okay too. Remember that there are a number of options out there that prevent pregnancy while not altering your natural hormone levels — condoms, diaphragms (if you wanna go old-school), and copper IUDs are solid options if that’s how you’re feeling. Bedsider has a great interface that walks you through all the birth control options on the market, and has a number of non-hormonal choices listed.

Do your research, and talk to your gynecologist, and if your gynecologist doesn’t get why you feel iffy about hormones, go and find one who does. Remember that it’s your body we’re talking about, so do what feels best for you.

Images: Monik Markus/Flickr; Giphy