The morning after pill, or emergency contraception (EC), is a medication taken after unprotected sexual intercourse or contraceptive failure to reduce the chance of pregnancy. It works primarily by delivering a high dose of hormones that temporarily delays or prevents the release of an egg from the ovary (ovulation). This hormonal intervention prevents fertilization, but it does not end a pregnancy that has already begun. Understanding the physical response to this hormonal surge provides clarity on what to expect and how long any effects may last.
Common Immediate Physical Effects
The introduction of a concentrated dose of hormones can lead to a range of temporary physical reactions. These immediate effects are generally mild and are a direct result of the medication. The most frequently reported feelings include nausea, which affects about one in five users, and sometimes vomiting.
Other short-lived symptoms include headache, dizziness, or a general feeling of fatigue. Some people also experience temporary breast tenderness or mild abdominal pain and cramping. These physical responses reflect the body’s adjustment to the sudden hormonal change.
Timeline for Symptom Resolution
For most people, the immediate physical side effects resolve quickly, often within 24 hours of taking the pill. It is uncommon for symptoms like nausea, headache, or dizziness to persist beyond one or two days. These side effects fade as the body processes and clears the high concentration of hormones from its system.
If nausea is a concern, taking the pill with food may help ease stomach upset. If vomiting occurs within two to three hours of taking the pill, consult a healthcare provider about the need for a second dose, as the pill may not have been fully absorbed. Using an over-the-counter pain reliever can help manage mild headaches or abdominal cramping during this short period.
Expected Changes to the Menstrual Cycle
The longest-lasting effect of emergency contraception is the temporary disruption to the subsequent menstrual cycle. Because the medication interferes with the hormonal signals that regulate ovulation, it can temporarily shift the timing of the next period. This alteration of the cycle is a sign that the medication has worked to delay or prevent ovulation.
The next period commonly arrives a few days earlier or later than expected, with delays of up to one week being normal. If the period is delayed by more than seven days, take a pregnancy test. The flow of the next period may also be different, possibly being lighter, heavier, or accompanied by irregular spotting or bleeding. These changes are temporary, and the cycle usually returns to its normal pattern the following month.
Warning Signs Requiring Medical Review
While most side effects are mild and transient, specific signs warrant immediate contact with a healthcare provider. Severe, ongoing lower abdominal pain, particularly three to five weeks after taking the pill, requires prompt medical attention. This could indicate an ectopic pregnancy, where a fertilized egg implants outside the uterus.
Unusually heavy or prolonged vaginal bleeding that is significantly different from a normal period, or spotting that continues until the next expected period, should also be reviewed by a professional. If symptoms such as a severe headache or stomach discomfort last for longer than a week, or if there is any sign of an allergic reaction like hives or difficulty breathing, seek medical advice quickly.