Milder Single Ingredient Birth Control Pills

When looking into birth control pills, many people are surprised by the fact that "I thought all pills were the same, but there are as many as two ingredients." Most oral contraceptives on the pharmacy shelf are combined preparations containing two hormones, estrogen and progestin. Recently, however, a pill composed of progestin alone, the so-called mini-pill, has also entered domestic pharmacies. In the clinic, those who are breastfeeding or who must avoid estrogen ask about this drug the most. Today, I will organize how a progestin-only preparation differs from a combined one, and for whom it becomes a suitable option.

The most fundamental difference between the two drugs is the number of hormones contained. The combined oral contraceptive commonly taken consists of two ingredients, estrogen and progestin, and even within combined preparations, the effect and side-effect pattern differ slightly depending on the type and content of the progestin derivative. By contrast, the progestin-only preparation, that is, the mini-pill, contains only one progestin, as the name says.

The single preparation available domestically mainly uses the desogestrel ingredient. By leaving out the estrogen ingredient entirely, this drug starts from the point that it can reduce some of the burden that can arise in relation to estrogen.

Which of the combined or single preparation suits you ultimately depends on how the ingredient difference interlocks with your own health condition. Looking together at the story of a milder single-ingredient birth control pill, which others with the same concern read, is helpful.

The single and combined preparations differ in the very way contraception is achieved. Traditional low-dose progestin-only preparations mainly thicken the cervical mucus and affect the endometrium and tubal motility to produce a contraceptive effect. By contrast, the desogestrel single preparation, in addition to this, has a prominent action of suppressing ovulation itself, as the UK's Faculty of Sexual and Reproductive Healthcare (FSRH, 2022) summarizes.

This difference has a very important meaning in actual use. The desogestrel single preparation, which suppresses ovulation, is reported to maintain ovulation suppression even if the dosing time is missed by up to 12 hours. So while time management is important for the single preparation as it is for the combined one, it has somewhat more leeway than the traditional single preparation.

Regarding the effectiveness figures, it is right to be honest. When taken exactly as directed, the contraceptive effect of the single preparation is reported to be at a high level, but studies directly comparing the effect with the two-ingredient combined preparation are still limited. In other words, there is not enough evidence to conclude that "the single preparation is stronger than the combined" or "weaker."

The situation in which the progestin-only preparation shines most clearly is right after delivery and while breastfeeding. Whereas combined preparations containing estrogen are not recommended for a certain period right after birth due to concerns about venous thrombosis risk and a decrease in breast milk volume, the progestin-only preparation is not contraindicated for breastfeeding and can be started relatively early after delivery, as the World Health Organization (WHO) and FSRH (2022) guide. The point that it is reported not to give a meaningful effect on the child's growth and development is also important information for breastfeeding mothers.

There are several situations besides breastfeeding in which estrogen must be avoided. Based on the UK Medical Eligibility Criteria (UKMEC, 2016), the single preparation is classified as a relatively suitable option for the following people.

• Those who have had venous thromboembolism or have a history of it (combined preparations are strongly restricted, but the single preparation is in a relatively usable category)
• Those who have migraine with aura (warning symptoms)
• Some conditions for which estrogen use is a burden, such as high blood pressure

That said, this classification is only a general standard, and whether it applies to you as is must be confirmed through care. If you want to know more deeply about thrombosis risk and the choice of pill ingredients, refer to why a consultation on birth control pills and thrombosis risk is needed, and if you are curious about the difference by type of estrogen, it is covered in more detail in the story of a new-ingredient pill with low thrombosis risk.

The single preparation differs from the combined one from the very dosing structure. Unlike the combined preparation, which commonly has a pill-free break after taking 21 tablets, the desogestrel single preparation is taken continuously, one tablet at the same time every day, for 28 tablets without a pill-free break. Those starting for the first time often get confused by the fact that there is no period of resting from the medicine in between.

The starting time is also set. When started on days 1 to 5 of the menstrual cycle, day 5 after a miscarriage, or day 21 after delivery, it is known that you can expect an effect right away without an additional contraceptive method. If started at another time, it is safer to use another contraceptive method together for the first few days.

The response to a missed dose is especially important with the single preparation. Combining FSRH (2022) and domestic approval information, if you notice within 12 hours of the set time, take one tablet immediately and take the next tablet at the original time. If you have passed 12 hours, take it as soon as you remember, but I recommend using another contraceptive method together for the following 7 days. The single preparation currently available is such that the effect declines if the dosing interval lengthens, so the habit of taking it at the same time is more important than anything.

Being a single preparation does not mean anyone can take it the same way without any restriction. Organizing the things checked in advance in the clinic:

In particular, the last interaction item is a part easy to miss if you do not attend to it yourself. Informing them, without omission, of the medicines, supplements, and herbal medicines you currently take at the prescription or purchase stage is the starting point of safe use.

The most commonly reported side effect with progestin-only preparations is breakthrough bleeding. Besides this, mood changes, headache, acne, and weight changes can appear, but the overall pattern is not greatly different from existing oral contraceptives.

Breakthrough bleeding is a symptom many people worry about, thinking "is the drug not suiting me," but in clinical experience, if you continue taking it, it usually tends to decrease over time. According to reports, the frequency decreases around 3 months and stabilizes considerably around 1 year. That said, if the bleeding pattern is severe or clearly different from usual, other causes must be examined together, so it is better to confirm through care than to self-judge. Regarding breakthrough bleeding while taking the pill, it is covered more concretely in oral contraceptives and how to handle breakthrough bleeding.

The progestin-only preparation, thanks to leaving out estrogen, becomes a meaningful option for those who are breastfeeding or must avoid estrogen. The point that it is reported not to greatly raise venous and arterial thrombosis risk, and the point that it is compatible with breastfeeding, are clear advantages. At the same time, you should know in a balanced way that taking it at the same time every day is important, that there is an adaptation process such as breakthrough bleeding, and that the evidence comparing the effect with the combined preparation is still limited.

What I most want to emphasize is that all birth control pills need thorough consultation before starting. There are separately those for whom the combined preparation suits, those for whom the single preparation suits, and those for whom another contraceptive method such as an intrauterine device is better. If you are looking into contraception for the first time, it is also good to look carefully, starting from what types of contraception there are.

Written by Lee Dong-hee, Director · OB-GYN specialist · See physician profile

First published December 10, 2023 · Last reviewed May 30, 2026

References: FSRH Guideline Progestogen-only Pills (2022), UK Medical Eligibility Criteria UKMEC (2016), WHO Medical Eligibility Criteria for Contraceptive Use (2015)

This article is intended to provide general health information and does not replace individual diagnosis or treatment. If you have symptoms, please consult through a medical visit.