ellaOne (ulipristal acetate 30 mg) is an emergency contraceptive pill taken within 120 hours (5 days) of unprotected intercourse to prevent pregnancy by delaying ovulation. Most reported side effects are mild and short-lived, with the most frequent being menstrual cycle changes, nausea, headaches, abdominal discomfort, and fatigue. While severe complications are rare, a period delayed by more than seven days or intense lower abdominal pain requires prompt medical assessment to rule out pregnancy or ectopic complications.
What Is ellaOne and How Does It Work?
ellaOne is a single-dose emergency morning-after pill containing ulipristal acetate (30 mg), a synthetic selective progesterone receptor modulator. Unlike traditional levonorgestrel-based emergency contraception, which is primary effective for up to 72 hours (3 days), ellaOne remains effective for up to 120 hours (5 days) after unprotected sex or birth control failure.
The primary mechanism of action involves delaying or inhibiting ovulation. By suppressing the surge of luteinizing hormone (LH), ellaOne prevents the ovary from releasing an egg during the window when sperm remain viable inside the reproductive tract. Because it alters hormone signaling to delay egg release, temporary hormonal symptoms and menstrual shifts are common after ingestion.
Most Common Side Effects of ellaOne
Clinical trial data indicates that the majority of women experience little to no disruption, or only mild side effects that resolve within 1 to 3 days. Below are the most frequently reported side effects.
Menstrual Cycle Changes and Bleeding
Because ulipristal acetate directly affects progesterone receptors, alterations to your menstrual cycle are the most expected reaction:
- Delayed or Early Period: Your next period may arrive several days earlier or later than anticipated. Clinical studies show that around 18.5% of users experience a period delayed by more than 7 days.
- Flow Variation: Menstrual bleeding may be noticeably heavier, lighter, or longer than your typical cycle.
- Intermenstrual Spotting: Unexpected light bleeding or breakthrough spotting can occur in the days following administration before your full period begins.
Gastrointestinal Discomfort
- Nausea: Feeling sick to the stomach affects roughly 1 in 10 users. Taking the tablet with a small snack or meal can help lessen stomach distress.
- Abdominal Cramping: Lower stomach pain or pelvic discomfort similar to menstrual cramps is frequently reported.
- Indigestion and Diarrhea: Less commonly, temporary digestive changes such as bloating, heartburn, or loose stools may occur.
Neurological and Systemic Reactions
- Headaches: Hormonal shifts can trigger mild to moderate tension headaches or migraines.
- Fatigue: Feeling unusually tired or sluggish for 24 to 48 hours after taking the pill is common.
- Dizziness: Mild lightheadedness can occur; sitting or lying down comfortably typically eases this symptom.
Mood and Breast Sensitivity
- Breast Tenderness: Increased breast soreness or swelling may persist until the next menstrual cycle.
- Mood Fluctuations: Temporary emotional changes, irritability, or mild mood swings can be triggered by sudden hormone shifts.
Overview of Side Effect Frequencies
| Category | Frequency | Common Side Effects |
| Very Common / Common | Affects up to 1 in 10 people | Nausea, abdominal pain, headache, dizziness, fatigue, dysmenorrhea (cramps), breast tenderness, muscle aches |
| Uncommon | Affects up to 1 in 100 people | Diarrhea, heartburn, dry mouth, flatulence, irregular vaginal bleeding, mood swings, anxiety, acne, hot flushes |
| Rare | Affects up to 1 in 1,000 people | Genital itching or pain, visual disturbances, disorientation, vertigo, fainting, hives, severe allergic reaction |
What to Do If You Vomit After Taking ellaOne
The active ingredient in ellaOne takes time to absorb into the bloodstream.
- Vomiting within 3 hours: If you vomit within 3 hours of swallowing the tablet, the medication may not have been fully absorbed, reducing or eliminating its effectiveness. You should contact a pharmacist or healthcare provider immediately to obtain a replacement dose.
- Vomiting after 3 hours: If vomiting occurs more than 3 hours after ingestion, the active drug has already been absorbed into your system, and a repeat dose is generally unnecessary.
Severe Symptoms: When to Seek Immediate Medical Attention
Although severe complications from ellaOne are rare, certain warning signs require immediate medical evaluation:
- Severe Lower Abdominal Pain: Intense pain on one side of the lower abdomen or pelvis—especially occurring 3 to 5 weeks after taking the pill—can be a sign of an ectopic pregnancy (a pregnancy developing outside the womb). Ectopic pregnancy is a medical emergency.
- Extremely Heavy Bleeding: Soaking through more than two sanitary pads or tampons per hour for two consecutive hours is abnormal and requires prompt clinical review.
- Allergic Reactions: Signs of a severe allergic reaction (anaphylaxis) include facial, lip, or tongue swelling, sudden skin rash/hives, and difficulty breathing or swallowing. Emergency services should be called immediately.
Frequently Asked Questions
How long do ellaOne side effects typically last?
Most side effects, such as nausea, headaches, dizziness, and fatigue, are mild and resolve within 24 to 72 hours after taking the tablet. Side effects related to the menstrual cycle, such as spotting or changes in bleeding intensity, may persist until your next period concludes, after which your cycle typically returns to its normal baseline.
Can ellaOne delay your period, and by how long?
Yes, delaying your period is one of the most common effects of ellaOne because the medication works specifically by postponing ovulation. For most women, the period arrives within 7 days of the expected date. However, clinical studies show that approximately 18% of users experience a delay longer than 7 days, and roughly 4% experience a delay exceeding 20 days.
What should I do if my period is more than a week late after taking ellaOne?
If your period is delayed by more than 7 days beyond its expected start date, you should perform an at-home pregnancy test. While ellaOne is up to 98% effective when taken promptly, no emergency contraceptive is 100% effective. If the test is negative but your period still does not arrive within another week, consult a healthcare professional for evaluation.
How does ellaOne differ from levonorgestrel (Levonelle / Plan B)?
ellaOne contains ulipristal acetate (30 mg) and remains highly effective for up to 120 hours (5 days) after unprotected sex, including during the window right before ovulation when luteinizing hormone levels rise. Levonorgestrel pills are effective for up to 72 hours (3 days) and lose efficacy sooner as ovulation approaches. Additionally, ellaOne requires a prescription in some regions and cannot be taken concurrently with regular progestin-containing hormonal contraceptives.
Does taking ellaOne affect future fertility or long-term health?
No. Research demonstrates that ellaOne has no long-term impact on overall health or future fertility. It functions strictly as a temporary emergency measure for a single menstrual cycle. Once your next menstrual period arrives, your natural fertility cycle resumes.
When should I take a pregnancy test after taking ellaOne?
You should take a pregnancy test if your period is more than 7 days late, if your bleeding is unusually light or short, or if it has been 21 days since the incident of unprotected intercourse and you have not yet experienced a normal menstrual period.