The phrase "late period pills" is not a formal medical term, but a colloquial one that can refer to several distinct types of medication used to address a delayed menstrual cycle. Understanding the differences between these options is critical for safety and making informed health decisions. These medications generally fall into three categories: progestin-based hormonal pills to induce menstruation, emergency contraception to prevent pregnancy, and medication abortion pills to end an early pregnancy.
Medications to Induce a Period (Menstrual Regulation)
The primary medical approach for inducing a period in non-pregnant individuals is through progestin-based therapy [1.3.1, 1.3.2]. These are prescription medications that a doctor might recommend for conditions like oligomenorrhea (infrequent periods) or amenorrhea (absence of periods) after confirming the person is not pregnant [1.3.1].
How They Work
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Pharmacology: Medications like norethindrone or medroxyprogesterone are synthetic forms of the hormone progesterone [1.3.1, 1.3.8]. A course of these pills is taken for a specified number of days (e.g., 5 to 10 days) to artificially elevate progesterone levels [1.3.7, 1.3.8]. When the medication is stopped, the sudden drop in progesterone signals the uterine lining (endometrium) to shed, resulting in a "withdrawal bleed" that mimics a period, typically within 3 to 7 days [1.3.2, 1.5.5].
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Purpose: This treatment is used to regulate the menstrual cycle when it's absent or irregular due to hormonal imbalances, not to terminate a pregnancy [1.3.8]. It is crucial to rule out pregnancy before starting this treatment, as it could potentially harm a developing baby [1.5.1].
Common Side Effects Side effects of progestin therapy can include [1.5.3, 1.5.6]:
- Irregular vaginal bleeding or spotting
- Headaches
- Nausea and bloating
- Breast tenderness
- Mood changes
- Weight changes
Emergency Contraception (The "Morning-After Pill")
Emergency Contraception (EC) is often mistakenly thought of as a "late period pill," but its function is to prevent pregnancy after unprotected sex or contraceptive failure, not to induce a period or end an established pregnancy [1.4.4, 1.4.6].
How It Works There are two main types of EC pills:
- Levonorgestrel (e.g., Plan B One-Step®): This pill contains a progestin called levonorgestrel and is most effective when taken as soon as possible, within 72 hours of unprotected sex [1.4.3]. It works primarily by preventing or delaying ovulation [1.4.3]. It is available over-the-counter [1.4.7].
- Ulipristal Acetate (e.g., ella®): This is a selective progesterone receptor modulator that can be taken up to 120 hours (5 days) after unprotected sex [1.6.7]. It works by delaying ovulation, even when taken closer to the time of ovulation than levonorgestrel [1.6.3]. It is more effective than levonorgestrel, especially between 72 and 120 hours after sex and for individuals with a higher BMI [1.6.2, 1.6.3]. Ulipristal acetate requires a prescription [1.6.4].
EC pills are not effective if you are already pregnant [1.4.6]. They may alter the timing of the next period, making it come earlier or later than expected [1.6.3].
Mifepristone and Misoprostol (Medication Abortion)
This combination of medications is what some sources explicitly refer to as "missed period pills" or "late period pills" [1.2.1, 1.2.2]. These are the same drugs used for a medication abortion to terminate a confirmed early pregnancy [1.2.1, 1.4.3]. However, the term "period pills" is also used to describe the practice of taking these medications to bring on a late period without first confirming pregnancy [1.2.3].
How They Work
- Mifepristone: This medication blocks the hormone progesterone, which is necessary to sustain a pregnancy. Without progesterone, the uterine lining breaks down [1.4.7].
- Misoprostol: This medication is taken after mifepristone and causes the uterus to cramp and empty, inducing bleeding to expel its contents [1.2.4, 1.4.7].
Whether a person is pregnant or not, this combination will cause cramping and bleeding, effectively inducing a period and ending a potential pregnancy if one exists [1.2.1, 1.2.4]. This practice is used as a form of fertility control in some parts of the world and is available via some telehealth clinicians in the U.S. [1.2.3, 1.2.4].
Comparison of "Late Period Pill" Options
| Medication Type | Primary Mechanism | Prescription Required? | Use Case | Key Distinction |
|---|---|---|---|---|
| Progestins (e.g., Norethindrone) | Causes a "withdrawal bleed" by altering hormone levels [1.3.2, 1.3.8] | Yes [1.3.1] | To regulate an irregular or absent period (non-pregnant) [1.3.8] | Does not terminate a pregnancy; pregnancy must be ruled out first [1.5.1]. |
| Emergency Contraception (e.g., Plan B, ella) | Prevents or delays ovulation to stop pregnancy from occurring [1.4.3, 1.6.3] | Levonorgestrel: No; Ulipristal Acetate: Yes [1.4.7] | Used after unprotected sex to prevent pregnancy [1.4.1] | Ineffective if pregnancy has already been established [1.4.6]. |
| Mifepristone & Misoprostol | Blocks progesterone and causes uterine contractions to empty the uterus [1.2.4, 1.4.7] | Yes [1.2.4] | To bring on a late period, ending a potential or confirmed early pregnancy [1.2.1, 1.2.4] | Terminates an existing pregnancy [1.4.4]. |
Conclusion
It is essential to understand that "late period pills" is a broad term for different medications with very different purposes. Consulting with a healthcare provider is the safest way to address a late period. A doctor can determine the cause of the delay—which could range from stress or hormonal imbalance to pregnancy—and recommend the appropriate and safe course of action. Self-medicating without a proper diagnosis can lead to ineffective treatment or serious health risks.
For more information on the distinction between emergency contraception and abortion pills, you can visit Planned Parenthood [1.4.6].
