Period Cramps: Why They Happen and What Actually Helps

Period cramps are your uterus, which is a muscle, squeezing to push out its lining, and they are usually a normal part of having periods. Heat, gentle movement and pain relief medicine started early all help, and cramps that stop you from doing your usual things are a reason to see a doctor, not something to push through.

Below this guide are the questions about cramps that readers have asked Soso, each with its answer.

Why cramps happen

Every period, chemicals called prostaglandins make the muscle of your uterus contract so it can shed its lining, which leaves your body as period blood. Strong contractions briefly cut down the blood flow to the muscle itself, and that is what hurts. Prostaglandins also turn up pain signals in general, which is why a crampy day can make everything feel more sore.

The pain is usually low in your belly, and for some people it spreads to the lower back or thighs. Prostaglandins peak around the start of bleeding and the first two to three days, so that is when cramps are usually worst. Not sure whether it is cramps or an ordinary stomachache? This guide to telling them apart helps.

How common cramps are, and when they start

Studies of teenagers have found period pain in anywhere from 16% to 93%, depending on who was asked and how. Severe pain is much less common, at 2% to 29%. So most teens do not have severe period pain, and if yours is severe, you are not imagining it.

Cramps often skip the very first periods. In the first year or two, most cycles do not release an egg, and the usual kind of period pain begins on average six to 12 months after a first period, when cycles that do release one get going. After that it tends to come back every cycle. Pain that starts much later is a different story, covered in the signs at the end.

Heat: simple, and it holds up

A heating pad or a hot water bottle on your lower belly is the easiest thing to try first. In a review of six randomised trials, the three that compared a heating pad with pain relief medicine found heat did at least as well, and better in some analyses. The catch is that these were few trials with small numbers of people. Wrap a hot water bottle in a towel so it feels warm, not hot, on your skin.

Moving helps, in two different ways

On a crampy day, light movement like stretching or a walk can help, even when curling up in bed feels like the only option.

Regular exercise is prevention, not rescue. In one review, the amount linked to less period pain was more than three sessions a week, longer than 30 minutes each, adding up to at least 90 minutes a week, kept up for at least 8 weeks. A separate review ranked relaxation exercise best at both 4 and 8 weeks, and every kind it studied reduced pain by 8 weeks. So pick whatever you will actually keep doing. Our guide to what helps when cramps hurt has more ideas.

Pain relief medicine works best early

Pain relief medicine works best when it is started one to two days before bleeding begins and continued through the first two to three days. That window follows the prostaglandin peak, so starting early gets ahead of the pain instead of chasing it.

An adult decides which medicine you take and how much, based on your age and weight, so ask a parent or another adult who looks after you rather than taking something on your own. Magnesium may help with period pain too, but the studies behind it are limited, and at this age food sources come before supplements, which are an adult's call as well.

When cramps are a reason to tell an adult

Cramps themselves are normal. These are not, and each one is worth telling a parent or another adult you trust so you can see a doctor:

• Pain that is much worse than usual, or that has not eased after the pain relief an adult gave you. Tell an adult straight away, not at the end of the day.
• Pain that is severe, or that keeps you from school, sport or friends. Among people with period pain, one third to one half miss school or work at least once per cycle, so you would not be the only one, but being stopped by pain is a reason to get help, not a test you are failing.
• Pain that starts much later than that usual six-to-12-month window, pelvic pain that keeps getting worse, or pain that comes with unusual bleeding or discharge.
• Very heavy bleeding: needing to change your pad every 1 to 2 hours, a period that lasts more than 7 days, clots bigger than about 2.5 cm, bleeding through to your clothes or bedding, or often feeling tired or short of breath. This counts from your very first period.

For more on what is and is not normal, see cramps, clots and other period symptoms.

Notes make that conversation easier, and they show you when to start pain relief next time, which is hard to guess while periods are still irregular. The Soso app has a daily log for cramps and flow if you want one place to keep them. The checked facts this guide relies on are listed below, each linked to its card on our medical sources.