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    Signs your period is coming (so you’re always prepared)

    Updated 23 November 2022 |
    Published 09 March 2022
    Fact Checked
    Medically reviewed by Dr. Jennifer Boyle, Obstetrician and gynecologist, Massachusetts General Hospital, Massachusetts, US
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    The body works in mysterious ways to alert you that your period is coming. We dive into some of the different signs so you’re never caught off guard.

    Even less fun than your actual period is the week or two of symptoms that many of us experience leading up to it. “Premenstrual syndrome,” which most of us know as PMS, is very common. In fact, nearly half of women experience PMS at some point in their lifetime. And while it looks different in everyone, PMS is thought to be caused by the same thing: fluctuating hormone levels throughout the menstrual cycle.

    The signs your period is coming aren’t the same for every person, and they can even change for an individual from month to month. For some, PMS symptoms are a minor annoyance, but for others, they can be debilitating. 

    You can use a period tracker like Flo, or our online period calculator to get an idea of when your next period might be due, but it's also worth delving into some of the physical signs your period may be on its way. That way, you know what to look out for so you don’t get caught short without your menstrual product of choice.

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    What is PMS?

    Knowing the signs your period is coming can help you handle your menstrual symptoms better. But first up: Why do we get PMS? According to the American College of Obstetricians and Gynecologists, PMS is a pattern of emotional and physical symptoms that happen regularly (at least three menstrual cycles in a row), interfere with a person’s normal life, strike in the 5 days before, and end within 4 days after a period starts.

    “Estrogen and progesterone are hormones that help control our menstrual cycle,” explains Amanda Kallen, MD, associate professor at Yale University School of Medicine of Reproductive Endocrinology and Infertility and Flo Medical Board expert. “These hormones fluctuate throughout a menstrual cycle: Estrogen is the dominant hormone before ovulation [your fertile window], and progesterone is dominant after ovulation [the days before your period starts]. This changing balance of hormones can contribute to PMS symptoms,” she explains. 

    What are the signs your period is coming?

    Let’s take a look at the common signs of PMS, which can be a clear indicator that your period is about to arrive.

    1. Your skin is breaking out

    Ever noticed how your skin is most breakout prone on the days you’re due? Yeah, it can be really annoying. But if solidarity helps you with this kind of thing, it might be useful to know that more than 50% of women say their acne symptoms get worse in the week before their period.

    “The rise in progesterone before a period can contribute to skin breakouts because it increases your skin’s production of sebum (oil) production,” explains Dr. Kallen. 

    2. Your breasts feel tender

    It’s common for breasts to feel extra sensitive, or even sore, on the days leading up to a period. “Breasts can feel sore and swollen due to the fluctuating levels of hormones,” explains Dr. Kallen. Why? “Estrogen enlarges breast ducts, and progesterone causes milk glands to swell. Both combined can make your breasts feel pretty tender.”

    Remember, it’s important to get to know how your breasts normally look and feel. Ideally, examine them in the days after your period ends, when your breasts are least likely to be swollen and tender. Bear in mind that breast tenderness before your period is normal, but if you have other concerns about your breasts or notice a change, you should see a health care professional.

    3. You have menstrual cramps

    Looking for signs your period is coming tomorrow? Menstrual cramps are a pretty good indicator. “Period-related stomach cramps are most likely caused by prostaglandins, hormone-like substances that tell your uterine muscles to contract (resulting in the shedding of the uterus lining) during your period,” Dr. Kallen explains. “Sometimes, those contracting muscles can create pain that radiates to your lower back.”

    Some people are more likely than others to experience these kinds of symptoms in the lead up to their period. One study on more than 3,000 women, published in the Journal of Women’s Health, found that those with higher levels of inflammation in the body during their monthly flow were more likely to experience cramps and back pain.

    But don’t always dismiss cramping as something that’s just part and parcel of having a period. If you’re experiencing pain that stops you from going about your day, speak to a health care professional. They can help you find ways to feel better and make sure the pain is not due to any other problem. “Severe lower back pain and cramping may even be associated with an underlying health condition, like endometriosis or uterine fibroids,” says Dr. Kallen.

    4. You’re having mood swings

    Ever find that you go from angry outbursts to anxiety attacks, then back to feeling emotionally stable — all in one day? If you notice your emotions are more intense than normal, this could also be a sign that your period is coming soon. 

    Emotional symptoms are thought to be connected to the rise and fall of hormones — particularly the dip in estrogen, which can make us feel low and irritable. “Some people may also be more susceptible to PMS due to underlying mood conditions or genetic factors,” says Dr. Kallen. 

    But if your PMS symptoms are intense and interfere with your daily life, it may be a sign of premenstrual dysphoric disorder (PMDD), a severe form of PMS. This often manifests in the form of anxiety or depression around the time of your period, and you can read more about the differences between PMS and PMDD here.

    5. You feel bloated

    Bloating is a completely normal, and admittedly uncomfortable, period symptom. “Bloating is triggered by fluctuating hormones — for instance, high levels of progesterone can slow the digestive tract, leading to constipation and bloating,” says Dr. Kallen. “Water retention may also be connected to changes in your diet around the time of your period, when you’re more likely to crave salty or sweet foods.”

    If your bloating symptoms persist even after your period has come and gone, it’s important to speak to a health care professional so they can rule out anything serious.

    6. You’re super tired

    If you’re feeling drained of energy and not sleeping well before your period starts, you’re definitely not alone. “Shifting hormones in the days before your period, as well as changes in your brain chemicals, can affect both your mood and sleep,” Dr. Kallen explains, noting that levels of serotonin, a brain chemical that affects mood, often decline along with falling estrogen levels

    Tiredness is also an early pregnancy sign due to high levels of progesterone — which plays a significant role in the first trimester as well as the second half of the menstrual cycle. And actually, many signs of early pregnancy — including cramping, mood swings, breast tenderness, and exhaustion — mimic the symptoms you typically experience before a period. “If there’s any chance of pregnancy, take a pregnancy test after a missed period,” Dr. Kallen says.  

    7. Your discharge is dry

    Vaginal discharge changes during different parts of your cycle — and is often a good telltale sign of the most fertile time in your cycle. “Around ovulation, your cervix produces more cervical mucus, and your discharge may have a raw egg white texture to increase the chances of conception,” explains Dr. Kallen. But right before your period, it generally looks different. “You’ll have no discharge at all, or it may be sticky because this is when you’re least fertile.”

    Signs your period is coming: The takeaway

    Everybody’s experience of PMS symptoms is unique. And let’s be honest: Managing PMS is not exactly a walk in the park. The good news is that most PMS symptoms should start to taper off as your period starts. 

    Tracking your cycle in Flo can be a useful tool for gathering information you can pass on to a doctor for a PMS or a PMDD diagnosis. It’s also a great way to gain more control over your cycle. It helps you understand when your next period is coming and enables you to understand what factors — like a lack of sleep or drinking too much coffee — may intensify PMS symptoms. Recognizing the signs can help you (mentally and physically) prepare for your next period, and it can allow you more time to listen to your body and practice a bit more self-care.


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    Yonkers, Kimberly Ann, et al. “Premenstrual Syndrome.” The Lancet, vol. 371, no. 9619, Apr. 2008, pp. 1200–10.

    History of updates

    Current version (23 November 2022)

    Medically reviewed by Dr. Jennifer Boyle, Obstetrician and gynecologist, Massachusetts General Hospital, Massachusetts, US

    Published (09 March 2022)

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