“The menstrual cycle is actually a vital sign,” says Seema Menon, MD, a gynecologist at Northwestern Medicine who specializes in pediatrics and adolescents. “This probably sounds like a bit of an overstatement, but periods that come too early, too late, too heavy or are painful can signal significant medical problems.”

Dr. Menon breaks down what some cycle irregularities might mean.

Periods That Start Too Early

If a period starts before age 8, it's a good idea to see a doctor. While this is often just an early start to normal puberty, it can also be a sign of something more serious.

Possible causes:

• Early but normal puberty (also called “precocious puberty”)
• Overactive thyroid gland (hyperthyroidism)
• Hormone imbalances
• Tumors of the ovary or brain

Early periods may signal that the body is maturing faster than usual. This early development may impact physical growth, emotional health and long-term reproductive health.

“The average age of starting a period is younger now than previous generations,” says Dr. Menon. “It may take two to three years for period cycles to come at monthly intervals. This can be due to a normal physiologic process or a medical condition similar to the causes of a delayed period.”

Research shows that in the United States, the average age for a first period (also called menarche) has dropped from 12.5 years to 11.9 years.

When Periods Come Too Late

Periods that come later than expected (primary amenorrhea) also deserve a closer look. “We define late as age 13 without development or age 15 with development,” says Dr. Menon.

Possible causes:

• Hormonal imbalance such as low estrogen
• Underactive thyroid gland (hypothyroidism)
• Polycystic ovary syndrome (PCOS)
• Structural issues like a blocked vagina, underdeveloped uterus or congenital (from birth) differences in the reproductive system
• Excessive exercise
• Being underweight or having a significant weight change (which may be related to an eating disorder)
• Chronic stress

Delayed periods may be a sign that the reproductive system isn’t developing as expected, which could affect fertility or bone health later in life.

Painful Periods

Menstrual cramps are common, but if a period causes severe pain — bad enough to miss school, sports or social activities  —  it should not be ignored.

Possible causes:

• Hormonal changes during early menstruation or other life stages
• Endometriosis, a condition where tissue grows outside of the uterus
• Structural problems with the uterus or vagina, such as a narrow cervix or blocked vaginal canal
• Uterine fibroids or cysts

“A lot of times, painful periods are age-related and can be treated very simply with hormone treatments,” says Dr. Menon.

When a Period Is Too Heavy

Periods that are so heavy (menorrhagia) that they soak through pads or tampons in less than two hours, or produce large blood clots, also should receive medical attention.

Possible causes:

• Bleeding disorders such as von Willebrand disease
• Uterine fibroids or polyps
• Side effects of certain medications
• Hormonal imbalance

Heavy periods that cause anemia (low iron levels) can be due to a bleeding disorder that requires treatment.

Next Steps

If you're an adolescent experiencing any of these irregularities with your period, or a parent noticing these in your child, don't just brush it off. It's a good idea to:

• Start a period tracker. Use an app or a simple calendar to note when your period starts, how long it lasts and how heavy it is. This information is helpful for your doctor.
• Talk to a trusted adult. Share your concerns with a parent, guardian, school nurse or another trusted adult. They can help you figure out what to do next.
• See a doctor. Make an appointment with a pediatrician, family physician or gynecologist. They can help determine if there's an underlying cause and guide you on the best course of action. They might ask about your diet, exercise, stress levels and family history.

Your period is a normal and healthy part of growing up, and it's also a powerful tool for understanding your body's overall health. Early attention to irregularities can lead to simple treatments, peace of mind and better long-term health.