Loestrin birth control: what is it, and who is it for?

Yael Cooperman, MD - Contributor Avatar

Reviewed by Yael Cooperman, MD, Ro, 

Written by Linnea Zielinski 

Yael Cooperman, MD - Contributor Avatar

Reviewed by Yael Cooperman, MD, Ro, 

Written by Linnea Zielinski 

last updated: May 12, 2021

4 min read

Your body is a magical machine, and every month, a delicate interplay between your brain, your uterus, and your ovaries makes sure that if everything goes as planned, an egg is released for potential fertilization and baby-making. But if baby-making isn’t in the cards for you right now, you can take a tiny pill every day to tell your brain, your uterus, and your ovaries “WHOA.” And like magic, your ovaries will hold up, and no egg will be released. 

So how does all this work? Let's take a look at one combined birth control option: Loestrin.

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How the pill works

All that communication telling your body not to release an egg relies on two main hormones: progesterone and estrogen. And that tiny pill? It contains both, just in synthetic forms (Berg, 2015). Progesterone tells your brain to tell your ovaries, “Not this month, ladies” (Kester, 2012). Research has also shown that it changes the cervical mucus (at the entrance to the uterus from the vagina), making it less hospitable to sperm (“um, bye.”) (Han, 2019).

So, where does estrogen come in? Well, it turns out that if you take just progesterone, you might experience something called breakthrough bleeding, which is when you get spotting throughout the month. So to avoid this, researchers added estrogen, which prevents that spotting (Speroff, 1982). Enter the combined oral contraceptive pills (progesterone combined with estrogen). 

But it doesn’t come without problems. It turns out that estrogen increases side effects (hey big, painful boobs) as well as the risk of dangerous blood clots (Martinelli, 2003).  

So researchers created an option with low levels of estrogen. And the star of those low-dose combined pills? Loestrin. It’s got the lowest available dose of estrogen of all combined OCPs.

What is Loestrin?

Low estrogen is the standout characteristic of Loestrin. Birth control pills all use synthetic forms of estrogen and progesterone, but there are several types of each. Loestrin uses a synthetic type of progesterone called norethisterone and an estrogen called Ethinyl estradiol. Some other brands of birth control use the same hormones, just in different amounts. Of all of the combined oral contraceptives available, Lo Loestrin Fe contains the smallest amount of estrogen. 

And while the low levels of estrogen are usually better tolerated than OCPs with higher estrogen levels, Loestrin still has side effects. The most common side effects are nausea, vomiting, headache, menstrual cramps, and changes in how you bleed during your period. Not everyone experiences the same changes, but Loestrin can make your period irregular or even cause heavier bleeding during your period. You may also notice that you break out more or gain weight while on the pill (FDA, 2010).

And low estrogen doesn’t mean no estrogen—no matter how low the estrogen quantities are in the pill, it still increases your risk of developing potentially dangerous blood clots. The risk is lower with Loestrin because it uses less estrogen, but that doesn’t eliminate the risk entirely.

How long does it take Loestrin to work?

The great news is that Leostrin can start working immediately as long as you start taking it at the beginning of your cycle (the first day you bleed) (NIH, 2017). Loestrin may also start working right away if you take it within the first week of your period (up to seven days after you start bleeding) (Schwartz, 2002). 

It’s still best for you to use barrier method protection like condoms the first week you take birth control pills (NIH, 2017). Birth control pills don’t prevent all pregnancies, but they are extremely effective. The better you are at taking birth control pills exactly as outlined in the instructions, the more effective they are—that means no forgetting the pill some days (Trussell, 2011).

But taking Loestrin is easy, especially if you set a reminder alarm on your phone. Like other birth control pills, Loestrin comes in packs of 28 pills. You take one pill a day in a particular order. When you take the last pill in a pack, you start a new pack the next day (FDA, 2010). You need to take Loestrin at the same time each day, though.

Who cannot take hormonal birth control?

For some people, the health risks of taking hormonal birth control outweigh the benefits. That’s the case for people who have health conditions that make it more likely that they’ll develop blood clots (DailyMed, 2017). So even though Loestrin has the lowest risk of OCPs because of its low estrogen, it’s still not a good option for people who have a history of blood clots.

Pills like Loestrin can also increase the risk of stroke in certain people. So if you’re over 35 and get migraines, have uncontrolled high blood pressure or diabetes, or smoke, you shouldn’t take them (Chang, 1999; Siritho, 2003). It’s also a good idea to talk to your healthcare provider about the safest birth control options if anyone in your family has had a heart attack or a stroke (Siritho, 2003).

If you’re nursing, you should not take oral contraceptives that contain estrogen. Talk to your healthcare provider about which birth control options are the best for people who are breastfeeding. They may suggest progesterone-only pills or an IUD (intrauterine device) (NIH, 2017).

So even if you can’t take hormonal birth control like Loestrin, you’re not out of options. Some forms of birth control don’t use hormones.

Non-hormonal birth control options

Sure, progestins tell your ovaries to cool it on producing eggs--but that’s not the only way to prevent pregnancy. The non-hormonal IUD, a small t-shaped device inserted into the uterus, presses pause on baby-making by making the uterus an inhospitable place for a fertilized egg (Ortiz, 1996).

Don’t forget about good ol’ condoms, either. When used properly, they’re very effective at preventing pregnancy and most sexually transmitted infections (STIs) (Holmes, 2004). You can also use spermicide with condoms to prevent pregnancy. 

Although some people stand by the rhythm method, it’s probably not your best bet. The rhythm method involves avoiding sexual intercourse during ovulation. Yes, ovulation is only a short window in your cycle, but that’s not the only factor here. 

Even if you don’t have sex when you’re ovulating, you can still get pregnant because sperm can survive for as long as 12 days (or more) in your reproductive tract (Morrison, 1972). Overall, far more people get pregnant each year using the rhythm method than the copper IUD (Klaus, 1982; Kaneshiro, 2010).


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

May 12, 2021

Written by

Linnea Zielinski

Fact checked by

Yael Cooperman, MD

About the medical reviewer

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.