ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

How Does the Morning After Pill Work and What Are the Side Effects?

Updated on August 11, 2014

What & How: Morning After Pill / Plan B / Next Choice

Heads up: this article is lengthy but thorough and sections are titled for easier access.

As someone who will not stop searching until my questions are answered, I’ve compiled all my findings about the Morning After Pill into one easy-to-read report for women like me who want more information and have had difficulty finding it. While there are other manufactures of the Morning After Pill, I’m going to use Plan B as the primary example in this article. You’ll find many of these pills contain most of the same ingredients and they all work toward the same purpose: to prevent pregnancy if you experience a little “oops”.

The issue with researching this topic online is that you're really not going to be able to find too much information on side effects from these pills because the effects vary from woman to woman and can vary in each individual any time she chooses to take it. However, this is an attempt to resolve that for you. The explanation will be lengthy only due to the breakdown and not because of complexity.

The affects can vary widely and are so dependent on cycle timing that’s it’s difficult to say how it will affect you, but not impossible. I’ve decided to do the work for you and here’s the gist (generalized and vague) of what you’ll find online, followed by what you might not find.


1. Plan B doeswork, regardless of where you are in your cycle (although nothing is ever 100% guaranteed.) Most women take it without need but to be safe (that little extra precaution) which is definitely fair when it comes to pregnancy prevention, as long as it's not used as the sole form of birth control.)

2. It will mess with your cycle (and emotions) in one way or another because of the large amount of hormones (called “progestin”) now in your system. Your body has to adjust your natural hormones to accommodate the progestin, and then readjust as it begins to leave your body.

3. This large dose of progestin will affect each woman differently depending on where her natural hormones were (cycle phase) at the time of taking Plan B, and those hormones will change (some increase, some decrease) throughout her cycle any given day/week/month.

Taking any morning after pill during different phases of the menstrual cycle will dictate side effects, and honestly the most paranoid side effect is whether or not your period will come sooner or later, as this is what every woman is waiting for. The other (rather annoying ones) are the pregnancy symptoms (and you will have them.)

I've learned that many of the women who take Plan B are unaware of what phase of their cycle they're actually in but that’s ok. It can be difficult to tell from one month to the next, unless you’ve been studying and journaling your body daily for several months or so. So I’m going to tell you how the morning after pill or Plan B will affect your cycle if taken before ovulation (follicular phase) and how it will affect your cycle if taken after ovulation (luteal phase).


Taking Plan B before you ovulate will actually inhibit ovulation, causing your next period to come later than usual (normally about 7-10 days later than you’d expect). The luteal phase normally lasts 10-14 days, starting with the first day of your period as Day 1. So what you’ve done is prolonged the luteal phase by delaying or interrupting when ovulation was going to occur. (This also means you’re not out of the “safe zone” for the month just yet, so using back-up contraception such as condoms and spermicide should serve you well. If I may, I’d also suggest making an appointment for extended birth control if your goal truly is to prevent pregnancy.)

This would mean that you should expect your period in about 3 weeks or so from the day you took the pill. If you feel concerned during the wait, it’s ok to take a HPT as no morning after pill should give you a false positive, (but false negatives can happen whether or not you’ve taken any birth control, so patience will be your best bet. I know, easier said than done.)


Now, if you take Plan B (or similar pill) after the luteal phase of your cycle, this should actually induce a period. Strange, I know. The significant increase and release of extra hormones in your body acts almost as a shock to your system and will cause a “pill-induced period”. It could happen within days and could last longer or shorter than normal; or the induced period could come at the 1-2 week mark you would expect during a normal cycle. However, it’s less likely to be later than usual. But again, keep in mind that most women aren’t precise with where they are in their cycle, even with a best guess, so again patience is key no matter how difficult that may be for now. (If you are more than a week later than usual, I would take a HPT &/or make an appointment with your doctor.)


Now what if you take a morning after pill during ovulation? Taking it during this time will not prevent the egg from being released. However, progestin can cause changes within your uterine lining (called the “endometrium”) making it more difficult for a fertilized egg to attach (which is called “implantation”) thus assisting in prevention of pregnancy and expelling the egg with your period as if fertilization had never occurred, (which can actually happen at any time in a woman’s life, although she usually doesn’t know it. The chance of pregnancy occurring for the average woman is about a 20% chance per month, which supports the theory that sometimes eggs are fertilized but do not attach, hence the term “chemical pregnancy”.)

Some research states that progestin taken through daily birth control pills can alter the endometrium somewhat during the menstrual month. However, some researchers disagree whether or not the amount of progestin found in morning after pills is significant enough to alter the endometrium and whether or not there’s enough time for the progestin to take that kind of effect. I’m not here to debate those studies. I’m only here to inform based upon my own knowledge through research.

However, based off online research, it appears researches have opposing opinions on this part of the subject due more to the “business” aspect than a physiological one. So let me make this very clear, morning after pills are not an abortifacient, meaning these are not abortion pills. Abortion pills cause the uterus to expel an embryo. Morning after pills are designed to prevent pregnancy altogether, just as in any other form of birth control.

So regardless of where you were in your cycle, you should have a period 1-3 weeks max after taking plan b whether or not it’s the pill induced period or your natural period (any period is a good sign whether longer or shorter than normal. You are encouraged to take a HPT or call your doctor at any time, especially if it’s been longer than 3 weeks since you took the pill.


Morning after pills can affect the following menstrual cycle as well. The date of the next (2nd) menstruation should be based off of the date of the plan b induced period rather than the date you would've normally expected it had you not taken plan b. (Plan b will change your cycle date, guaranteed.)

No one can really say how long a woman will feel the effects from plan b, as far as the change in her cycle. Also, many women tend to pay extra attention to bodily changes during this time, and I honestly believe they tend to notice things that have always been there that they may not have noticed before. On top of that, adding the side effects of the pill. What a mental mess, let alone a physical one!

However, it’s unlikely that the "pregnancy symptoms" associated with Plan B would be prominent after more than 2-3 weeks, maximum. If it’s been 3 weeks and the symptoms are still there and you still haven’t had your period, you definitely need to take a HPT &/or call your doctor.

It's difficult to determine how morning after pills affect the next ovulation cycle. There are no public studies on when to expect your next ovulation, so many professionals still do not know if a women would ovulate sooner, later, or on time for that next awaited cycle. The only advice on that one is to use other forms of birth control every time you engage in sexual activity, if you truly want to avoid pregnancy.

Until I create an article, there are plenty of online websites that can teach you how to read your own body by feeling the cervix at different times of your cycle but it's logical to know that it can take several months of monitoring your body before you could actually feel the difference and know whether or not you are in your fertile window. Doesn't hurt to learn and this is almost a sure-fire way of knowing when you are fertile, for prevention or planning.

God bless!

*Disclaimer: All information contained within the article is intended for informational purposes only and is not intended to be taken in place of advice from Medical Health Professionals or Emergency Personnel Professionals* By visiting this page, you acknowledge you have read and are in agreement with this disclaimer and the author will not be held liable in any way.* Health concerns should be taken seriously and your health care provider should be contacted for evaluation and diagnosis. In the case of an emergency, please contact 911 immediately.*



    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)