Emergency Contraception Calculator
Choose your method and enter the hours since intercourse to see effectiveness rates and recommendations.
When you need emergency contraception, the I-Pill often comes up first, but it’s not the only option on the table. This guide breaks down how the I-Pill (levonorgestrel) measures up against the most common alternatives - Ulipristal acetate (Ella), the copper IUD, and the older Yuzpe regimen - so you can pick the method that fits your timing, health profile, and peace of mind.
What the I-Pill (Levonorgestrel) Actually Is
I-Pill is a single-dose emergency contraceptive tablet that contains 1.5 mg of levonorgestrel, a synthetic progestin. It works primarily by delaying ovulation, thereby preventing fertilisation when taken within 72 hours of unprotected sex. Levonorgestrel was first approved for emergency use in the UK in 1999 and has become the go‑to over‑the‑counter pill for many because it’s cheap, readily available, and has a well‑documented safety record.
Typical effectiveness ranges from 85 % when taken within 24 hours to about 58 % at the 72‑hour mark. The sooner you take it, the better the odds of avoiding pregnancy.
Alternative #1: Ulipristal Acetate (Ella)
Ulipristal acetate, marketed as Ella, is a selective progesterone receptor modulator (SPRM) approved for emergency contraception up to 120 hours (5 days) after intercourse. A single 30 mg tablet works by strongly inhibiting or postponing ovulation, even when the LH surge has already started.
Effectiveness stays above 85 % throughout the full five‑day window, making it the most reliable pill‑based emergency option compared with levonorgestrel.
Alternative #2: Copper Intrauterine Device (IUD)
Copper IUD is a small, T‑shaped device inserted into the uterus within five days of unprotected intercourse. The copper ions create a spermicidal environment and also prevent implantation. It is the most effective form of emergency contraception, with a failure rate of less than 0.1 %.
Beyond emergency use, the copper IUD offers up to ten years of ongoing contraception, making it a long‑term solution for many.
Alternative #3: Yuzpe Regimen (Combined Estrogen/Progestin)
The Yuzpe method uses two doses of combined oral contraceptive pills (containing both estrogen and progestin) taken 12 hours apart, started within 72 hours of intercourse. While it can be used when other options are unavailable, its effectiveness is lower (around 75 %) and side‑effects such as nausea are more common.
How to Choose the Right Method: Decision Factors
- Time since intercourse: If you’re beyond 72 hours, only Ulipristal, copper IUD, or a copper‑based method work.
- Medical history: Women with a history of hormone‑sensitive conditions (e.g., breast cancer) may prefer the copper IUD, which is hormone‑free.
- Future contraception needs: If you want ongoing birth control, the copper IUD kills two birds with one stone.
- Access and cost: I‑Pill and Ella are over‑the‑counter in many pharmacies; copper IUD insertion requires a clinician and can be more expensive upfront.
- Side‑effect tolerance: Levonorgestrel can cause mild nausea; Ulipristal may cause headache; copper IUD may cause heavier periods.
Side‑Effect Profile at a Glance
| Method | Typical Side‑Effects | Serious Risks |
|---|---|---|
| I‑Pill (Levonorgestrel) | Nausea, mild abdominal cramping, fatigue | Very rare allergic reaction |
| Ulipristal acetate (Ella) | Headache, dizziness, nausea | Potential drug‑interaction with CYP3A4 inhibitors |
| Copper IUD | Increased menstrual bleeding, cramping for first 1‑2 months | Uterine perforation (extremely rare) |
| Yuzpe regimen | Nausea, vomiting, breast tenderness | Thromboembolic events (very low) |
Effectiveness Comparison
| Method | Within 24 h | Within 72 h | Up to 120 h |
|---|---|---|---|
| I‑Pill (Levonorgestrel) | 15 % failure | 42 % failure | - |
| Ulipristal acetate (Ella) | 12 % failure | 22 % failure | 15 % failure |
| Copper IUD | 0.1 % failure | 0.1 % failure | 0.1 % failure |
| Yuzpe regimen | 25 % failure | 25 % failure | - |
Numbers reflect real‑world studies published in the British Medical Journal and the European Journal of Contraception. The copper IUD consistently outperforms all pill‑based options, while Ulipristal offers the best balance of timing flexibility and effectiveness among oral pills.
Practical Tips for Using Each Method
- I‑Pill: Take the whole tablet as soon as possible after the event. If you’re prone to nausea, a light snack can help. No follow‑up doctor visit is required.
- Ulipristal acetate: Purchase from a pharmacy (prescription not required in the UK). Do not take any hormonal contraception for five days after use, as it may reduce efficacy.
- Copper IUD: Schedule a same‑day appointment with a qualified clinician. Bring a clean urine sample for pregnancy testing before insertion.
- Yuzpe regimen: Follow the dosing schedule precisely (two doses 12 hours apart). Take anti‑emetic medication if you’re prone to vomiting to ensure absorption.
When to Seek Professional Advice
If you experience any of the following, contact a healthcare provider immediately:
- Severe abdominal pain lasting more than 24 hours
- Signs of an allergic reaction (hives, swelling, difficulty breathing)
- Persistent heavy bleeding after IUD insertion
- Uncertainty about pregnancy status - take a home pregnancy test 14 days after emergency contraception
Bottom Line: Which One Is Right for You?
For most people who act quickly, the I-Pill is a convenient, low‑cost choice. If you’re beyond the 72‑hour window or want the highest possible protection, Ulipristal acetate or a copper IUD should be your go‑to. Women who prefer a hormone‑free method or who also need long‑term contraception will find the copper IUD the most attractive option. And if you only have combined oral contraceptives on hand, the Yuzpe regimen can serve as a backup, though it’s less effective.
Frequently Asked Questions
How soon after sex should I take the I‑Pill?
The earlier, the better. It’s most effective within the first 24 hours and still works up to 72 hours, though effectiveness drops the longer you wait.
Can I use the I‑Pill and my regular birth control at the same time?
Yes. The I‑Pill does not interfere with ongoing hormonal contraceptives. If you start a new pack after taking the I‑Pill, follow the usual start‑day instructions for that method.
Is the copper IUD safe for teenagers?
Yes, it’s approved for use in adolescents. The insertion procedure is the same, and the long‑term protection can be especially helpful for young people who want to avoid daily pills.
What drugs interact with Ulipristal acetate?
Medications that strongly induce CYP3A4 enzymes (e.g., rifampicin, certain anti‑epileptics, St John’s wort) can reduce Ella’s effectiveness. Talk to a pharmacist if you’re on any of these.
Can I become pregnant after emergency contraception?
If the emergency method works as intended, the chance of pregnancy is very low. However, if you miss a period or have any pregnancy symptoms, take a home test or see a clinician.
Choosing the right emergency contraceptive is about timing, health considerations, and personal preference. Armed with the facts above, you can make an informed decision that fits your lifestyle and gives you the confidence you deserve.
