Postinor-2 Side Effects: Is it Safe?

Key Takeaways

• Postinor-2 is safe when used correctly. It’s an effective emergency contraceptive designed to prevent pregnancy when taken within 72 hours after unprotected sex.
• Mild, short-term side effects like nausea, fatigue, or period irregularities are common.
• Your period may come earlier, later, heavier, or lighter after taking Postinor-2.
• Postinor-2 doesn’t cause infertility, as it only delays ovulation and doesn’t have long-term effects on reproductive health when used reserved for emergencies.
• It’s not for regular use. Repeated use can disrupt your menstrual cycle and cause a hormonal imbalance.
• It’s not an STI protection; condoms are still necessary in this case.
• Seek medical advice if your period is more than two weeks late, you experience severe abdominal pain, or have a history of ectopic pregnancy or liver disease.

You’re probably here because you’ve either recently taken Postinor-2 and are now wondering what side effects might happen. Or, you’ve just had unprotected sex and are trying to figure out whether the side effects are worth taking the pill.

Quick answer is: your body might react to Postinor-2 for a while due to the strong hormones it contains. But that doesn’t always mean something dangerous is happening. Postinor-2 should be a safe emergency contraceptive when taken correctly.

Here, we’ll walk you through how your body might respond after taking the pills, so you can understand what’s normal, what to expect over the next few days, and when it’s necessary to reconsider other contraceptive options.

What is Postinor-2?

Before jumping to the side effects of Postinor-2, let’s first understand what it actually is.

Postinor-2, or the morning-after pill, is an emergency contraceptive that comes in a pack of two tablets. Each contains 0.75 mg of levonorgestrel, a synthetic progestin that works by delaying or preventing ovulation.

It’s always recommended to take it as soon as possible after unprotected sex, as its effectiveness drops the longer you wait. Here’s the full breakdown:

• Within 24 hours: up to 95% effective.
• Between 24 and 48 hours: approximately 85% effective.
• Between 48 and 72 hours: effectiveness drops to 58%.

While Postinor-2 is available over-the-counter in many regions, you’ll need a doctor’s prescription to get it in Singapore. Many clinics, however, offer discreet online consultations, and the pills can be delivered straight to your doorstep.

How to Use Postinor-2 Correctly

With the right uses, Postinor-2 can be significantly effective in preventing pregnancy. Here’s what you need to know:

Dosing Instructions

Each pack of Postinor-2 contains two tablets, each with 0.75 mg of levonorgestrel. There are two ways you can take them:

• Two-dose method: Take the first pill as soon as possible after having unprotected sex, followed by the second pill 12 hours later.
• Single-dose method: Take both pills at the same time, right after unprotected sex. Make sure not to exceed the 72-hour window period.

Missing or Vomiting a Dose?

If you follow the two-dose method and forget to take another pill after 12 hours, you can take it as soon as you remember, provided it’s still within 72 hours after unprotected sex.

On the other hand, if you vomit after taking either one or both pills, here’s what you need to do:

• If you vomited within three hours of taking the tablet, you should take another tablet 

Safety Precautions

Postinor-2 is meant for occasional, emergency use only. For regular contraception, you may want to explore other reliable options such as birth control pills, IUDs, implants, or hormonal patches.

Additionally, it doesn’t protect against sexually transmitted infections. In this case, condoms are still the best protection.

Last, consult your doctor if you’re on certain medications like antibiotics, epilepsy drugs, or consuming St. John’s Wort—as taking them may reduce the effectiveness of Postinor-2.

Common Postinor-2 Side Effects

Now that we’ve covered what Postinor-2 is and how it works, let’s talk about the side effects.

Since Postinor-2 contains strong hormones from levonorgestrel, it can trigger changes in your body. Everyone reacts differently—some feel stronger symptoms, while others barely notice anything.

The good news is, these effects are usually mild and temporary:

• Nausea
• Headache
• Fatigue
• Breast tenderness
• Abdominal pain
• Vomiting

Aside from physical reactions from taking Postinor-2, there are other changes you should also know. In the next sections, we’ll discuss how it may affect your period and whether or not it causes infertility.

Side Effects of Postinor-2 on Menstruation

Since Postinor-2 delivers strong progestin hormones to your body, changes affecting your menstrual cycle are expected. These can be seen in the timing and duration of your period, menstrual flow, as well as the cycle pattern.

Here’s the further breakdown:

Delayed or Early Period

Taking the morning-after pill can affect the timing of your next period. It may come earlier or later than usual. How is this possible?

If you take Postinor-2 after ovulation, the sudden hormone surge can make your body shed the uterine lining sooner. As a result, your next period may come earlier than expected.

On the other hand, if you take Postinor-2 before ovulation, it can delay ovulation. Since ovulation determines when your next period starts, this delay also means your period will likely come later than usual.

Lighter or Heavier Bleeding

Postinor-2 can also change the amount of bleeding during your next period. Some may notice a lighter flow, while others have a heavier bleeding.

These changes happen because the high dose of levonorgestrel can temporarily disrupt your hormonal balance. This affects how your uterine lining builds up and sheds. As a result, your next period may look slightly different from what you usually experience.

How does the uterine lining affect period flow? Here’s what actually happens:

• Lighter flow: Your next period might be lighter due to the hormone surge, which can cause early shedding or incomplete buildup of the uterine lining. As a result, there’s less tissue to release, making your period appear lighter.
• Heavier flow: The hormone surge can also cause the uterine lining to thicken, especially when taken before ovulation. This may lead to a heavier flow and, in some cases, stronger cramps.

Spotting

Aside from affecting period flow, taking the morning-after pill can also cause spotting. It’s among the common side effects of Postinor-2 on the menstrual cycle, which shouldn’t be a cause of concern.

The spotting usually happens a few days after taking the pills. This isn’t your actual period. Instead, it’s a temporary reaction to the sudden hormone surge, and it typically goes away on its own within a few days.

Notes:

Side effects of Postinor-2 on menstruation mostly last only for one cycle, which means your usual cycle will return to normal within 4-6 weeks. If your period is late for more than 2 weeks, it’s a good idea to take a pregnancy test. Consult your doctor as well if period irregularities continue beyond the next cycle.

Postinor-2 and Infertility Concerns

The effects of levonorgestrel emergency contraception on women’s fertility have long been widely discussed. Many think that taking Postinor-2 would lead to side effects that cause infertility in the long run.

The fact is, Postinor-2 doesn’t cause infertility. It works only by delaying or preventing ovulation, without permanently changing your reproductive system. Once the hormones from the pills leave your body, your cycle and fertility will gradually return to normal.

There are, however, rare cases of ectopic pregnancy associated with Postinor-2 uses, but that doesn’t mean the pills are to blame. If fertilisation happened before taking it, the thickened uterine lining from Postinor-2 may stop the egg from implanting in the uterus, causing it to attach elsewhere, usually in the fallopian tube.

Consult your doctor if you experience severe abdominal pain, unusual bleeding, or if your period is more than a week late after taking Postinor-2.

Postinor-2 Effectiveness and Limitations

Postinor-2 use has been proven effective in preventing pregnancy. It’s a reliable form of emergency contraception for situations when you’re worried your regular birth control might not have worked or when it was missed or forgotten.

However, its effectiveness depends greatly on timing. The pill must be taken within 72 hours after unprotected sex. The sooner you take it, the higher its success rate, as its efficacy decreases over time. Here’s the breakdown of its efficacy over time:

• Within 24 hours: up to 95% effective.
• Between 24 and 48 hours: approximately 85% effective.
• Between 48 and 72 hours: effectiveness drops to 58%.

There are also other factors that can affect how well Postinor-2 works, including body composition and interactions with other drugs.

Postinor-2 may be less effective in women with higher body weight, mainly due to how the body absorbs and processes the hormone. Still, it offers better protection against unwanted pregnancy than not taking anything at all.

Consuming some medications can also reduce Postinor-2 effectiveness. These include antibiotics, epilepsy drugs, and herbal supplements like St. John’s Wort.

Last but not least, Postinor-2 may not protect from an unwanted pregnancy with multiple unprotected sex in the same cycle. This is because the pill only delays ovulation temporarily, and once its effect wears off, you could still ovulate later in the same cycle.

Who Should Avoid Postinor-2?

Postinor-2 is generally safe for preventing unwanted pregnancy after unprotected sexual intercourse. However, its use should be carefully considered with the following conditions:

• Certain medication consumption: Women who take antibiotics, epilepsy drugs, or herbal supplements like St. John’s Wort should consult a doctor before use. These medications can interfere with how Postinor-2 works, affecting its effectiveness.
• Pre-existing medical conditions: Those with liver disease, a history of ectopic pregnancy, or unexplained vaginal bleeding should seek medical advice before taking Postinor-2, ensuring that it’s safe to use without increasing the risk of complications.

Even if you don’t have any of these conditions, regular use of Postinor-2 should be avoided. Taking it frequently can disrupt your menstrual cycle, cause irregular bleeding or spotting, and is associated with higher hormone levels than regular contraceptives.

Disclaimer: These are for general informational purposes only and do not replace advice from your doctor or pharmacist.

Looking for more information on contraceptive options and women’s health? Check out our comprehensive guides on birth control pills, contraceptive patch, and delay menses pills to compare different ways to manage your cycle and contraception needs. For urgent contraception, you might find our page on emergency contraceptives useful.

Finally, if you’re interested in maintaining reproductive wellness or scheduling routine care, explore our women’s health screening services for personalized check-ups and preventive care.

We’re here to support your health journey — feel free to reach out with any questions or to book a consultation.

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