Periods hurt because your uterus physically contracts to shed its lining, and the chemicals driving those contractions also trigger pain. The process is essentially the same mechanism behind any muscle cramp, but it happens in a place with dense nerve endings, which makes the sensation hard to ignore. For most people, this pain is a normal part of menstruation. For some, it signals something more going on.
How Your Uterus Creates Pain
Each month, the lining of your uterus thickens in preparation for a possible pregnancy. When pregnancy doesn’t happen, your body releases chemicals called prostaglandins that tell the uterine muscle to contract and push out that lining. These contractions squeeze the blood vessels that supply the uterus, temporarily cutting off oxygen to the tissue. That oxygen deprivation is what produces the cramping pain you feel, similar to what happens when any muscle works hard without enough blood flow.
The more prostaglandins your body produces, the stronger the contractions and the worse the pain. This is why some people have mild, barely noticeable cramps while others are doubled over. Prostaglandin levels vary significantly from person to person and even cycle to cycle. They also don’t stay in the uterus: excess prostaglandins can spill into the bloodstream, which explains why period pain often comes with nausea, fatigue, bloating, and a general feeling of being unwell.
What Normal Period Pain Feels Like
Typical menstrual cramps, what doctors call primary dysmenorrhea, produce a recurrent, crampy pain in the lower abdomen that starts just before or at the beginning of your period and lasts two to three days. The pain often radiates into the lower back and thighs. This type of pain usually begins six to 12 months after a person’s first period and tends to peak in the late teens or early twenties. It often becomes less intense with age, and particularly after childbirth.
Primary dysmenorrhea is extremely common and doesn’t indicate any underlying problem. The pain is real, sometimes severe, but it’s caused purely by the mechanics of shedding the uterine lining. A pelvic exam in someone with primary dysmenorrhea comes back completely normal.
When Pain Points to Something Else
Period pain that starts later in life, changes significantly in intensity, or doesn’t follow the usual pattern can be a sign of an underlying condition. This is called secondary dysmenorrhea, and it results from a structural or tissue-level problem in the pelvis.
The most common culprits include:
- Endometriosis: Tissue similar to the uterine lining grows outside the uterus, on the ovaries, fallopian tubes, or pelvic walls. This tissue responds to hormonal changes the same way the uterine lining does: it thickens, breaks down, and bleeds each cycle. But because it has no way to leave the body, it causes inflammation, scarring, and intense pain.
- Adenomyosis: The uterine lining grows into the muscular wall of the uterus itself. During each cycle, this embedded tissue swells and bleeds within the muscle, causing the uterus to enlarge and periods to become both heavier and more painful. The condition is driven by estrogen and often coexists with endometriosis and fibroids.
- Uterine fibroids: Noncancerous growths in or on the uterine wall can distort the shape of the uterus, increase its surface area, and intensify both cramping and bleeding.
Clues that your pain may fall into this category include bleeding between periods, pain during sex, periods that suddenly become much heavier or more painful than they used to be, and pain that persists outside of menstruation. An ultrasound is typically the first step in checking for these conditions.
Signs Your Pain Needs Attention
Period pain exists on a spectrum, and there’s no universal cutoff for “too much.” But certain patterns are worth flagging. If pain is severe enough to regularly keep you home from work or school, that alone is reason to get evaluated. The same goes if you need to change your pad or tampon every one to two hours, if you’re using two types of period products at the same time to manage flow, or if you’re experiencing migraines timed to your cycle.
Pain that doesn’t respond to over-the-counter painkillers, pain that has gotten progressively worse over several cycles, or pain that started for the first time well into your twenties or thirties all warrant a conversation with a doctor. These patterns don’t necessarily mean something is wrong, but they’re the ones most likely to have a treatable cause.
Why Anti-Inflammatory Painkillers Work
Since prostaglandins are the direct cause of menstrual cramping, the most effective pain relief targets prostaglandin production. Anti-inflammatory painkillers like ibuprofen and naproxen work by blocking the enzyme your body uses to make prostaglandins in the first place. Fewer prostaglandins means weaker contractions, better blood flow to the uterine muscle, and less pain.
Timing matters more than most people realize. These medications work best when taken before prostaglandin levels peak, which means starting at the first sign of cramping or even a few hours before your period typically begins. Waiting until the pain is already intense means prostaglandins have already been released, and the medication is playing catch-up.
Heat Therapy as an Alternative
A heating pad on your lower abdomen isn’t just comforting. It’s genuinely effective. A 2025 meta-analysis in Frontiers in Medicine pooled data from 22 randomized trials involving nearly 2,000 women and found that heat therapy provided pain relief comparable to, or slightly better than, anti-inflammatory painkillers after three months of use. Even within the first 24 hours, heat performed on par with medication.
The safety difference was notable: heat therapy reduced the risk of side effects by about 70% compared to anti-inflammatory drugs. For people who get stomach irritation from painkillers, or who simply prefer not to take medication, a heating pad at around 40°C (104°F) applied to the lower abdomen is a well-supported option. Combining heat with medication is also reasonable for people whose cramps don’t respond fully to either approach alone.
Other Approaches That Help
Exercise is one of the more counterintuitive recommendations, since moving is the last thing most people want to do when cramping. But physical activity increases blood flow to the pelvis, releases the body’s natural painkillers, and can reduce the intensity of contractions. Even a 20-minute walk or gentle stretching can make a noticeable difference.
Hormonal birth control is often used for people whose cramps are severe and recurring. By thinning the uterine lining or preventing ovulation, these methods reduce the amount of tissue that needs to be shed each cycle, which in turn lowers prostaglandin production. The result is lighter, less painful periods, or in some cases, no period at all. For secondary dysmenorrhea caused by conditions like endometriosis or adenomyosis, treatment focuses on managing the underlying condition itself, which may involve hormonal therapy, procedures, or in some cases, surgery.