While both are effective emergency contraceptives, Ella is significantly more effective. Ella is 65% more effective at preventing pregnancy than Plan B, when it's taken within 24 hours. If taken within 72 hours, Ella is still 42% more effective than Plan B. Ella works during a longer window (five days vs. three days) and is less affected by BMI.
Feature |
Ella |
Plan B and other forms of levonorgestrel |
Active ingredient |
Ulipristal acetate |
Levonorgestrel |
Effectiveness Window |
Up to 5 days (120 hours) |
Best within 72 hours |
Method of action |
Delays/prevents ovulation and thickens cervical mucus, making it harder for sperm to pass through |
Delays/prevents ovulation and thickens cervical mucus, making it harder for sperm to pass through |
Effectiveness with BMI |
Highly effective for a BMI of less than 35, possibly reduced effectiveness with a BMI of over 35 |
Reduced effectiveness with a BMI of over 30 |
Prescription status |
Requires prescription |
Available over-the-counter, with generic levonorgestrel available by prescription |
Potential side effects |
Nausea, abdominal pain, fatigue, headache |
Nausea, abdominal pain, fatigue, headache |
Medication interactions |
Certain medications can reduce effectiveness |
Fewer medication interactions compared to Ella |