Plan B One-Step contains a single 1.5 mg dose of levonorgestrel as the active ingredient.
Shoppers reach for this emergency pill in a hurry, so let’s get the basics straight from the start. The product is a one-tablet pack. That tablet holds levonorgestrel, a progestin used for emergency birth control. The dose is fixed at 1.5 milligrams in the standard brand and its true generics. No measuring, no split dosing, no calculators.
Levonorgestrel Amount In Plan B One-Step: What The Label Says
The drug facts panel and the official labeling both point to the same number: a single 1.5 mg tablet. This is the full amount taken once, as soon as possible after sex when no regular protection was used or something failed. Older two-tablet packs existed in some markets years back; each of those smaller tablets delivered 0.75 mg, taken 12 hours apart. The modern single-tablet pack replaced that schedule for simplicity and to cut missed second doses.
Why The Single 1.5 Mg Tablet Became Standard
One pill lowers the chances of a missed dose, and pharmacies can stock fewer variants. For the user, it’s clearer: buy a box, swallow the tablet, and you’re done. That streamlines access, which matters when timing affects how well this method works.
Emergency Contraception Options At A Glance
The levonorgestrel pill is common in pharmacies. Other options exist with different contents and windows. Here’s a quick, wide view you can scan before reading deeper.
| Option | What It Contains | Usual Timing Window |
|---|---|---|
| Levonorgestrel single tablet | 1.5 mg levonorgestrel | Best within 72 hours; may help up to 120 hours |
| Ulipristal acetate tablet | 30 mg ulipristal acetate | Up to 120 hours, Rx in many places |
| Copper IUD placed by a clinician | Copper (non-hormonal) | Up to 5 days; ongoing contraception |
How The Pill Works In Plain Language
This progestin can delay or block the surge that triggers ovulation. If the egg isn’t released yet, sperm can’t meet it. That mechanism is time-sensitive, which is why swallowing the tablet soon after sex gives better odds. If ovulation already happened, this method may not help. It does not end a pregnancy and it isn’t the same as mifepristone-misoprostol care. Brands and generics with the same dose act the same way in this context.
What The Dose Does In Your Body
After you swallow the tablet, levonorgestrel absorbs fast. Peak levels arrive within a few hours for most users. The body then clears it across the next day or two. Some people may feel brief nausea, a short-term change in the next period’s timing, or mild spotting. These pass on their own for most users.
Brand, Generic, And Look-Alike Products
Pharmacies carry the brand and several authorized or true generics. All list 1.5 mg levonorgestrel on the front. Packaging colors vary, and store brands often sit next to the brand box. Read the active ingredient line on the label, not just the brand name or color pattern. If the front says 1.5 mg levonorgestrel and the directions say take one tablet by mouth once, you’re holding the same dose class.
How To Spot Real Generics
Real generics list the same active ingredient and the same strength. They carry the same use directions. They don’t say “dietary supplement,” and they don’t hide the strength on the back panel. If you find a product with an herbal blend or a vague promise without a milligram listing, put it back.
Timing, Effectiveness, And Practical Steps
Time matters. Swallow the tablet as soon as you can. Many users set a reminder for the next period date and keep the box or a photo of the lot number until bleeding arrives. If the period is more than a week late, take a pregnancy test. Back-up condoms or a barrier method during the same cycle can help manage risk after the dose. For user guidance on windows and choices, see ACOG’s emergency contraception FAQ.
Expected Effectiveness By Hour Range
Real-world studies show the odds of preventing pregnancy are highest in the first three days after sex and trend downward after that. The window often cited runs up to 120 hours, though the curve drops with each day. Body weight and the timing of ovulation also shape outcomes, which is why a clinician may suggest ulipristal acetate or a copper IUD in some cases.
Safety, Side Effects, And Interactions
This method is used by many people without a clinic visit. Side effects are usually mild and short-lived. Nausea, a brief headache, breast tenderness, or a day of dizziness can appear. If you vomit within two hours, call a pharmacist about taking another tablet. If pain is severe on one side of the lower belly, seek urgent care to rule out other causes.
Medicines That Can Weaken The Effect
Some drugs speed up the enzymes that clear levonorgestrel. That can lower levels before the pill does its job. Examples include some seizure medicines, rifampin, some antiretroviral regimens, and St. John’s wort. If you use any of these, ask a clinician about ulipristal or an IUD for that episode, since they may hold up better in the face of those interactions.
Weight, BMI, And Dose Questions
Data on weight and this method’s performance are mixed. Some analyses suggest lower odds at higher body mass. Guidance bodies still list the 1.5 mg tablet as an option for all weights, with the note that ulipristal or a copper IUD may work better for some users. Talk to a clinician if you want a plan that fits your body and your timeline.
What To Expect With Your Period
Bleeding can come a few days early or late. Flow can be lighter or heavier than usual. Mild cramps are common. If the period is late by a week or more, take a test. If bleeding is very heavy or you feel faint, seek care. Keep using your usual birth control going forward, or start a new method right away if a clinician says that method fits your needs. A same-day start helps avoid another anxious pharmacy run.
Reading The Label: Lines That Matter
When you pick up a box, scan for a few specifics so you know you have the right product and you use it well.
The Front Panel
Look for “levonorgestrel 1.5 mg.” That line tells you it is the single-dose class. Find the “one tablet, one dose” note. If you see two tablets with complex timing, you may be holding an older schedule or a different product entirely.
The Directions
They should say: take one tablet by mouth as soon as possible within 72 hours after sex. The fine print often adds that it may still help up to 120 hours. If you vomit soon after swallowing, you may need another tablet.
Warnings And When Not To Use
This method doesn’t protect against STIs. It is for occasional use, not a regular birth control plan. If you’re already pregnant, this pill won’t work on that pregnancy. If you have unexplained bleeding, pelvic pain, or fainting, talk to a clinician.
When Another Method Fits Better
Sometimes a different option makes more sense. If it’s been four to five days and ovulation may be near, a clinician may suggest ulipristal. If you want a back-up that also gives long-term contraception, a copper IUD placed within five days is the gold-standard for that situation. Both routes can cut risk later in the cycle. A same-day clinic call can clarify which route suits your timing and health history.
Cost, Access, And Privacy Tips
Many pharmacies keep the boxes on open shelves near the family planning aisle. Stores may lock them in a clear case to deter theft; a staff member can unlock the case without judging your purchase. Prices vary by brand. Store brands are often cheaper and contain the same active ingredient and dose. Some clinics and health departments offer low-cost or free doses. Many places allow people of any age to buy the box without a prescription.
How To Store A “Just In Case” Box
Keep the box in a cool, dry spot, away from direct sun. Check the expiration date twice a year. If you carry it in a bag, avoid hot cars. A sealed blister pack holds up well in a drawer or medicine cabinet for months.
When To Test Or Call A Clinician
Use a home pregnancy test if your period is a week late. If the test is positive, book care. If bleeding is heavy or pain is sharp on one side, seek urgent help. If you take medicines that can change hormone levels, ask a pharmacist or clinician about the best back-up for next time. If you need long-term contraception, a same-day start on pills, a ring, a patch, a shot, an implant, or an IUD can end the cycle of pharmacy runs.
Quick Reference: Dose, Window, And Choices
Here’s a second table you can use when talking with a clinician or standing in the aisle. It repeats the key dose and timing points, side by side with the other common route so you can compare fast.
| Method | Single Dose | Best Use Window |
|---|---|---|
| Levonorgestrel pill | 1.5 mg once | ASAP; best within 72 h; may help to 120 h |
| Ulipristal acetate | 30 mg once | Up to 120 h |
| Copper IUD | N/A (device) | Up to 5 days; then ongoing prevention |
How We Keep This Page Accurate
This page pulls dose and use facts from current, recognized sources and checks them against the package labeling. For dose strength and single-tablet directions, see the FDA drug label for the brand. For timing ranges, mechanism, and alternate methods, see guidance from leading professional groups.
For official dose and use details, see the FDA label for the brand. For patient-friendly guidance on choices and timing, see ACOG’s emergency contraception FAQ.