Plan B (levonorgestrel): How it works and when to take it

Birth Control Options ...Emergency Contraceptio...

1 Jan

Q: If I had unprotected sex last night (or the condom broke), how soon do I need to take Plan B for it to actually work—and is it still worth taking if it’s been like 2–3 days?

A: Take Plan B as fast as you can. The sooner you take it after unprotected sex, the better it works. It’s most effective within 24 hours, still solid up to 72 hours (3 days), and may offer some protection up to 120 hours (5 days), but the effectiveness keeps dropping with time.

If it’s been 2–3 days: yes, it’s still worth taking Plan B, especially if you’re not already super close to or past ovulation. If it’s been more than 3 days, a copper IUD or a different emergency pill (like ella/ulipristal) may work better if you can get access quickly.

Bottom line: don’t overthink it, act fast, then make a backup plan.

If your brain is spiraling and you want to talk through timing, symptoms, or your cycle, you can always hop into Gush and vent it all out with someone who actually listens.

How soon should you take Plan B after unprotected sex for it to work?

How Plan B actually works in your body

Plan B (levonorgestrel) is emergency contraception, not the abortion pill. It works mainly by delaying or blocking ovulation — the moment your ovary releases an egg.

Here’s the big picture:

Sperm can hang out in your reproductive tract for up to 5 days.
You can only get pregnant if an egg is present during that time.
Plan B floods your body with a synthetic progestin, which tells your brain, “Nope, not ovulation time,” and pushes that egg release back.

If ovulation is delayed long enough, the sperm die off before they ever meet an egg. No egg, no fertilization, no pregnancy.

If ovulation already happened before you took Plan B, it doesn’t work well — because there’s nothing left for it to delay.

Timing: hour‑by‑hour reality

Let’s talk numbers, not fear-mongering:

Within 24 hours: This is the sweet spot. Studies show Plan B can reduce the risk of pregnancy by up to ~95% when taken in the first day.
Within 72 hours (3 days): Still considered effective, but that protection drops — more like 52–85%, depending on where you were in your cycle.
72–120 hours (3–5 days): Levonorgestrel is less reliable here. Some data say it can still do something, especially if ovulation hasn’t happened yet, but it’s not the top-choice option.

So if last night’s condom betrayal happened and you’re reading this now? Do not wait until some perfect time. The clock is not on your team; taking Plan B is.

Want help sorting out where you are in your cycle and how high the odds actually are for you? Your body doesn’t have to fit a textbook to matter. Drop what you know (and what you don’t) into Gush and talk it through with someone who speaks fluent PMS and panic.

What if it’s already been 2–3 days?

If you’re 48–72 hours out, here’s the deal:

Yes, it’s still worth taking Plan B.
It’s less effective than in the first 24 hours, but it still significantly lowers your chance of pregnancy.
Effectiveness also depends on whether you were close to ovulation (more on that in a second).

A simple way to think about it:

Day 1 (within 24h): Best case.
Day 2–3: Still absolutely recommended.
Day 4–5: Plan B might help, but other emergency contraception is usually better.

If a doctor, clinic, or pharmacy can get you ella (ulipristal acetate) within 5 days, it tends to work better later in the window and closer to ovulation than Plan B.

What if it’s been more than 3 days since unprotected sex?

If you’re past the 72-hour mark, you have options — and you deserve to know them all, not just whatever’s on the drugstore shelf.

Two stronger emergency contraception options:

Ella (ulipristal acetate)
- Works up to 120 hours (5 days) after unprotected sex.
- More effective than Plan B, especially closer to ovulation.
- Requires a prescription in a lot of places.
Copper IUD (Paragard)
- Can be inserted up to 5 days after unprotected sex.
- Is the most effective form of emergency contraception.
- Then keeps working as birth control for up to 10+ years.

If you can’t access those quickly, many people still choose to take Plan B after 3 days because some protection feels better than zero. Just know it’s not working at full strength anymore.

How Plan B interacts with your menstrual cycle

To really understand timing, you need the cycle breakdown your high school health class skipped.

A “typical” 28-day cycle has four main phases:

Menstrual phase (Days 1–5ish)
- You’re bleeding. Hormones (estrogen and progesterone) are low.
- Your brain starts releasing FSH (follicle-stimulating hormone) to grow new follicles in your ovaries.
Follicular phase (Days 1–13)
- Estrogen rises as follicles grow.
- One follicle becomes dominant — that’s the one that will release an egg.
- You might notice fertile signs starting: wetter discharge, more energy.
Ovulation (Around Day 14, but wildly variable)
- A surge of LH (luteinizing hormone) from your brain triggers the ovary to release that egg.
- This egg only lives about 12–24 hours.
- Fertile window = about 5 days before ovulation + the day of ovulation.
Luteal phase (Days 15–28)
- The empty follicle becomes the corpus luteum, which pumps out progesterone.
- Progesterone thickens your uterine lining and calms the system.
- If no pregnancy, progesterone drops → lining sheds → next period.

Where Plan B does its thing:

It mainly works in the late follicular phase, before the LH surge fully kicks off and before ovulation happens.
If you’re already solidly in the luteal phase (after ovulation), Plan B doesn’t do much to stop pregnancy because the egg already had its shot at meeting sperm.

Irregular cycles, birth control mishaps, and real life

Now for the messy reality: most people’s cycles do not run on a clean 28‑day schedule.

Pregnancy risk is higher when:

Your unprotected sex happened in the 5 days before ovulation or the day of ovulation.
You usually have regular cycles and know you were mid‑cycle.
You had super fertile cervical mucus (clear, stretchy, egg‑white‑like).

Risk is usually lower when:

You had unprotected sex during your real period or right before it.
You tend to have longer cycles and were early in the follicular phase.

If you’re on hormonal birth control (pill, patch, ring) and missed doses or had a screw‑up:

Plan B is often still recommended as backup.
Your cycle signs (discharge, timing) may be less predictable because synthetic hormones override your natural rhythm.

No matter where you land — irregular cycles, chaotic schedules, partner who “doesn’t like condoms” (dump him) — you deserve real information, not shame.

If your situation is a little bit chaos, a little bit “I have no idea where I am in my cycle,” you’re not broken — you’re human. Walk through what happened, day by day, with Gush and get a reality check that’s based on your body, not scare tactics.

What to do next after taking Plan B

Once you’ve taken the pill:

Mark the date you had unprotected sex and the date you took Plan B.
Expect your next period to come up to a week early or late.
Take a pregnancy test:
- About 3 weeks after the unprotected sex, or
- 1 week after your period should have arrived.

Also use backup contraception (condoms, abstain, or start consistent hormonal birth control) for the rest of this cycle. Plan B is a fire extinguisher, not a long‑term plan.

You’re not “reckless” for needing emergency contraception. You’re living in a world that refuses to give women honest sex ed or easy access to protection, then blames us when biology does what biology does.

Q: Does Plan B still work if I’m already close to ovulating or I have a higher body weight/ BMI? I keep seeing conflicting info online and it’s stressing me out.

A: Plan B works best before your body starts the final hormonal countdown to ovulation. If you’re early‑ to mid‑cycle, it can be very effective. If you’re right at or just past ovulation, Plan B may not work well because its main job is to delay egg release — and that ship may have already sailed.

Body weight and BMI do matter: research shows Plan B can be less effective for people over about 165 lbs (75 kg), and especially over ~176–195 lbs (80–88 kg). That doesn’t mean it does nothing; it means the failure risk is higher.

If you’re near ovulation and in a higher weight range, options like ella (ulipristal) or a copper IUD are usually better bets if you can get them quickly.

If you’re trying to decode ovulation signs, weight, and effectiveness without losing your mind, you’re exactly who we built Gush for — bring your chaos chart and we’ll untangle it with you.

Does Plan B work if you’re ovulating or have a higher BMI?

Plan B and ovulation: where the line really is

Plan B’s main move is delaying ovulation. That means timing is everything.

Here’s the breakdown:

Before the LH surge (early–mid follicular phase):
- Plan B can effectively stall the egg from being released.
- This is when it works best.
Right before ovulation (late follicular, LH surge already starting):
- Plan B may or may not be able to stop the egg in time.
- Effectiveness drops the closer you are to the actual ovulation moment.
During or after ovulation (luteal phase):
- If the egg has already been released, Plan B can’t “un‑ovulate” you.
- There’s little to no evidence it stops a fertilized egg from implanting.
- Translation: once ovulation has happened, Plan B is basically late to the party.

So when people say “Plan B doesn’t work if you’re ovulating,” what they really mean is: if ovulation has already occurred or is literally happening, its power is limited.

How to tell where you are in your cycle (realistically)

Textbook cycles are cute. Real bodies are messy. Let’s map it out anyway.

Typical 28‑ish day cycle phases:

Menstrual phase (bleeding)
- Hormones low; uterus is shedding.
- Pregnancy risk is usually low, but not always zero — especially if you have very short cycles.
Follicular phase (pre‑ovulation)
- Estrogen is rising.
- Discharge gets wetter, creamier.
- You might feel more social, more energized.
Ovulation window
- LH surges → triggers egg release.
- Cervical mucus becomes very slippery, clear, stretchy (egg‑white vibes).
- Libido often spikes.
Luteal phase (post‑ovulation)
- Progesterone rises.
- Body temp is a bit higher.
- You may feel calmer at first, then PMS gremlins show up.

If unprotected sex happens in the 5 days before ovulation or on ovulation day, that’s the highest risk window. Plan B is working against the clock here.

If you’re not tracking your cycle with an app, temps, or ovulation tests, you’re guessing — and that’s okay. Most people are. That’s why urgent options like ella and copper IUDs exist.

If your body is sending mixed signals (irregular periods, hormonal birth control, PCOS, stress), you don’t have to magically become a fertility scientist overnight. Dump your symptoms and timing into Gush and let someone help you make sense of it without judgment.

Plan B effectiveness and higher body weight/BMI

Here’s the part most people weren’t told at the pharmacy counter.

Research suggests levonorgestrel emergency contraception (Plan B and generics) is less effective at higher weights/BMIs:

Effectiveness starts to noticeably drop above ~165 lbs (75 kg).
Some studies show a much higher risk of failure above ~176–195 lbs (80–88 kg) or BMI ≥ 30.

Does that mean it’s useless if you’re in a bigger body? No.

It means the chance of pregnancy is higher compared to someone under those weight thresholds.
Many clinicians still recommend taking Plan B if it’s what you can get right now, rather than doing nothing.

The real problem isn’t your weight — it’s a system that:

Designed dosing around smaller bodies.
Didn’t bother telling the rest of us.

Your body is not the issue. The research and access gaps are.

Better emergency contraception options for higher BMI or near ovulation

If you:

Have a higher body weight/BMI and/or
Think you were close to ovulation when you had unprotected sex,

…then these options are generally more effective than Plan B:

Ella (ulipristal acetate)
- Works up to 5 days after unprotected sex.
- More effective than Plan B at every time point.
- Works better in people with higher body weight than levonorgestrel, though extremely high BMI may still impact it.
- Needs a prescription in many places, but some telehealth services will do rapid scripts.
Copper IUD (Paragard)
- The most effective emergency contraception we have.
- Works up to 5 days after unprotected sex, and sometimes longer depending on ovulation timing.
- Actually toxic to sperm — it wrecks their vibe and makes fertilization very unlikely.
- Not impacted by body weight.
- Then doubles as long‑term birth control.

If those aren’t accessible the same day and Plan B is sitting on a shelf in front of you, most providers would say: take Plan B now, then still try to get ella or a copper IUD if possible, depending on timing.

How hormones, weight, and Plan B intersect

Why does weight even matter here? Short version: pharmacokinetics — how your body absorbs, distributes, and breaks down the drug.

A one‑size‑fits‑all dose of levonorgestrel may lead to lower effective levels in people with larger body mass.
That can blunt its ability to stop the LH surge and delay ovulation.

Meanwhile, your normal cycle hormones are doing their own circus act:

Estrogen climbs pre‑ovulation, pushing follicles to mature.
LH spikes, shouting “release the egg.”
Plan B tries to shout louder with synthetic progestin to stall that process.

If:

You’re smaller-bodied and early‑cycle → Plan B usually wins that shouting match.
You’re larger-bodied and at peak fertile window → LH may overpower what the single levonorgestrel dose can do.

Again: that doesn’t mean your body is the problem. It means the dose was never tailored to you.

Where irregular cycles and birth control fit in

If your cycle is irregular because of:

PCOS
Thyroid issues
Stress, under‑eating, over‑training
Recently coming off hormonal birth control

…then timing ovulation is even harder. You might:

Ovulate late
Skip ovulation some cycles
Have super long follicular phases

In those cases, clinicians often lean even harder on ella or copper IUDs as the gold standard emergency contraception, especially if pregnancy would be a major crisis.

If you’re on the pill/patch/ring and:

Missed multiple doses
Started a new pack late
Had antibiotics plus diarrhea/vomiting

…Plan B can still be used, but your baseline hormones are being controlled by synthetic ones, so cycle tracking signs (like mucus) aren’t very reliable.

You deserve more than “just take this pill and hope.” You deserve context, probabilities, and real options.

Q: What side effects are normal after taking Plan B (nausea, spotting, late/early period), and when should I take a pregnancy test or call a doctor if my period is weird?

A: Normal Plan B side effects can include nausea, fatigue, dizziness, breast tenderness, mild cramps, a headache, and changes in your bleeding — like spotting, a slightly heavier or lighter period, or your period coming up to a week earlier or later than usual.

The red flags: severe abdominal pain, very heavy bleeding (soaking through more than 2 pads an hour for several hours), signs of an allergic reaction, or no period at all within 3 weeks of taking Plan B. Those all deserve medical attention.

For pregnancy testing: take one about 3 weeks after the unprotected sex that led you to take Plan B, or 1 week after your period should have started if it’s late.

If you’re stuck in “is this normal or am I pregnant?” hell, you’re not alone — bring your symptoms and timeline to Gush and unpack it with someone who won’t brush you off.

Normal Plan B side effects, period changes, and when to worry

Common Plan B side effects you might notice

Levonorgestrel is a high dose of synthetic progestin, so your body is getting hit with a hormone wave. Completely expected reactions include:

Nausea
Fatigue or feeling wiped out
Dizziness or lightheadedness
Headache
Breast tenderness or soreness
Mild to moderate cramps
Bloating
Moodiness or feeling off

Most of these side effects:

Show up within the first 24–48 hours.
Fade on their own within a couple days.

If you vomit within 2 hours of taking the pill, that’s a problem — your body might not have absorbed it. In that case, you usually need another dose or a different form of emergency contraception. A clinic, urgent care, or telehealth service can walk you through that.

What Plan B can do to your period

This is where everyone panics — because the first sign of pregnancy is also a “weird period.” But Plan B itself can change your bleeding pattern.

Totally normal after Plan B:

Your period comes up to 1 week earlier than usual.
Your period is up to 1 week late.
You spot or have light bleeding a few days after taking it.
Your bleed is heavier or lighter than what you’re used to.

Why? Hormones.

Your menstrual cycle is run by a relay team of chemicals:

Estrogen builds your uterine lining.
Progesterone stabilizes it after ovulation.
FSH & LH control follicle growth and ovulation.

Plan B drops a spike of synthetic progestin into that system.

If you take it before ovulation, it can delay ovulation → your period may come later.
If you take it after ovulation, it can still tweak how your lining behaves → cue spotting or an earlier/lighter bleed.

That doesn’t automatically mean pregnancy. It means your body just got hormonally whiplashed and is recalibrating.

If your cycle never fits the “normal” chart and every change sends you into doom scroll mode, you’re not dramatic — you’re under‑informed by a system that trained you to doubt your own body. Dump your cycle chaos into Gush and let someone walk through what’s likely hormone chaos vs what might need a test or check‑up.

What’s normal vs. concerning bleeding after Plan B

Let’s separate annoying from alarming.

Annoying but usually normal:

Light spotting for a few days.
A random one‑day mini bleed.
A period that’s heavier than usual but still manageable with your normal pads/tampons.
Mild cramping.

Concerning and deserves medical care:

Bleeding so heavy you’re soaking more than 2 pads or tampons per hour for several hours.
Passing very large clots repeatedly.
Feeling faint, short of breath, or like you might pass out with the bleeding.

That level of bleeding can signal serious issues — including anemia or, rarely, complications unrelated to Plan B.

When to take a pregnancy test after Plan B

Pregnancy tests need time. If you test too early, you can get a false sense of security.

Best timing:

Three weeks after the unprotected sex that led you to take Plan B, or
At least 1 week after your period should have started if it’s late.

Use a high‑sensitivity urine test (most modern home tests are) with first‑morning pee if you can.

If the test is:

Negative, and you got a period afterward: pregnancy is very unlikely.
Negative, but no period and you’re freaking out: test again in 5–7 days or get a blood test.
Positive: you’re pregnant, and Plan B did not work this time. It does not cause birth defects. From there, your options depend on your local laws and your personal choice.

When to call a doctor or clinic after Plan B

You do not need a check‑up just because you used Plan B. But you should get medical help if you notice:

No period within 3 weeks after taking it.
Severe lower abdominal pain, especially on one side.
Very heavy bleeding (more than 2 pads an hour for several hours).
Persistent nausea/vomiting beyond the first couple days.
Signs of allergic reaction (swelling, trouble breathing, hives).

Severe one‑sided abdominal pain with spotting or faintness could mean ectopic pregnancy (a pregnancy outside the uterus). That’s rare, but dangerous, and needs urgent care.

You deserve to be taken seriously when you walk into a clinic — not dismissed with “it’s probably fine.” If anyone minimizes your pain or concern, that’s about them, not you.

How Plan B collides with your cycle hormones

To understand the weirdness, zoom out to the cycle again:

Before ovulation (follicular phase):
- Estrogen is rising.
- Plan B may delay ovulation, shifting the whole timeline.
- Your next period might come later than usual.
Around ovulation:
- LH is surging.
- Plan B tries to slam the brakes on egg release.
- Hormonal tug‑of‑war = spotting, cramps, mood swings.
After ovulation (luteal phase):
- Progesterone is already high.
- Plan B might slightly destabilize the lining.
- You could see earlier bleeding or a shorter cycle.

If you:

Just came off the pill
Have PCOS or irregular cycles
Are under high stress or big life changes

…your hormones are already improvising. Plan B is one more layer, so your cycle may take a month or two to feel “normal” again.

How hormonal birth control and Plan B interact

If you’re already on hormonal birth control and took Plan B because of a mistake (missed pills, condom broke, late ring/patch replacement):

Keep taking your regular birth control as directed (or start the next pack on time).
Use backup (condoms) for at least 7 days after you restart or correct your method.
Your bleeding may be extra chaotic this cycle — because you’ve got your usual synthetic hormones plus levonorgestrel.

Plan B does not:

Ruin your fertility.
Make future cycles permanently irregular.
Build up in your body long‑term.

It’s a short, sharp hormone spike. Annoying? Yes. Permanent damage? No.

Your fear is valid. Your body’s weird reaction is valid. And you get to demand clarity, not condescension.

People Often Ask

Can I take Plan B more than once in the same month?

Using Plan B multiple times in a month is not dangerous in the sense of poisoning you, but it’s not ideal as a regular birth control plan. Each dose is a big hormone blast. Repeating it can lead to:

Totally chaotic cycles (spotting, late/early periods)
Stronger side effects (nausea, mood swings, cramps)

More importantly, Plan B is less effective than consistent methods like the pill, IUD, implant, or ring. If you’ve needed it more than once in a few months, that’s your sign the real problem is access to reliable birth control, not your “irresponsibility.”

Talk to a clinic or telehealth service about getting a long‑term method that actually fits your life. And if you want to sort through options without judgment, you can always drag the whole situation into Gush first.

Does Plan B affect my fertility long term?

No. Plan B does not cause infertility or long‑term damage to your reproductive system. It temporarily tweaks your hormones to delay ovulation for one cycle, then your body goes back to its usual programming.

What it does not do:

Burn out your ovaries
Reduce your future egg count
Make it harder to get pregnant later

You could technically get pregnant as soon as you ovulate again after taking it — which might be in the very next cycle. If anyone told you Plan B “ruins your chances of having kids,” they’re wrong or fear‑mongering.

Short‑term hormonal chaos? Totally. Permanent fertility damage? No. If your cycles stay wildly off for months, that’s something to explore — but the root cause is almost never a single dose of Plan B.

Is Plan B the same as the abortion pill?

No. Plan B and the abortion pill are completely different things.

Plan B (levonorgestrel) is emergency contraception. It works before pregnancy happens, mainly by delaying ovulation so sperm never meet an egg.
The so‑called "abortion pill" is usually a combo of mifepristone + misoprostol, which works after a pregnancy has already implanted in the uterus.

Plan B doesn’t:

End an existing pregnancy
Harm an implanted embryo
Cause an abortion

Politicians and bad‑faith commentators blur this on purpose to scare and confuse people. Don’t let them win. Knowing the difference is part of protecting your rights — and your sanity.

Can I drink alcohol after taking Plan B?

Alcohol doesn’t cancel out Plan B or make it stop working. If you’ve already taken the pill and then drink later, you’re not undoing the emergency contraception.

The real concern is vomiting:

If you throw up within 2 hours of taking Plan B (from alcohol or anything else), your body may not have absorbed it fully.
In that case, you usually need another dose or a different method — that’s a good moment to call a clinic or urgent care.

Also, alcohol + anxiety + hormones is a rough combo. Your body is already processing a lot; being gentle with it for at least a day or two isn’t a bad idea.

How often is “too often” to use Plan B?

There’s no hard cap where your body suddenly breaks, but using Plan B frequently (like multiple times per year) is a sign something else needs fixing — usually access to steady birth control or a partner who respects condoms.

Using it now and then is okay. Using it as your main method:

Means more side effects and unpredictable cycles
Still doesn’t protect you as well from pregnancy as regular contraception
Does nothing for STIs

If you’re stuck in a cycle of emergency contraception because the system makes real birth control hard to get, that’s not a personal failure — that’s structural violence dressed up as “policy.” In the meantime, if you want to untangle patterns, options, and what you actually want your plan to be, you can always talk it out with Gush.

If you’re still side‑eyeing your body, your bleeding, or your odds, you don’t have to sit with that alone. When you want to ask the awkward questions, unpack weird patterns, or just sanity‑check whether something is normal, slide into Gush and get real talk instead of judgment.

Lauren Hanson