Is a 28-day cycle 'normal', and is mine abnormal if it is not exactly 28?

No. Anywhere from 24 to 38 days between the first day of one period and the first day of the next is normal. Twenty-eight is just an average. What matters more is whether your own cycle stays fairly consistent month to month.

How many days of bleeding is normal?

Up to about 8 days, with 2 to 7 days being typical. Bleeding that regularly lasts longer than 8 days is considered prolonged and worth discussing with a clinician.

How do I know if my period is too heavy?

Warning signs include soaking through a pad or tampon every hour for several hours, changing protection during the night, passing clots the size of a quarter or larger, doubling up on protection, or bleeding that limits your normal activities. Feeling tired or short of breath can signal blood loss heavy enough to cause anemia.

My cycle length changes by a few days each month. Is that a problem?

Small variation is normal, up to about 7 days of month-to-month difference (a bit more, up to 9 days, in the teen years and around ages 42 to 45). Larger or unpredictable swings can point to ovulation problems and are worth evaluating.

I spotted between periods. Should I worry?

Any bleeding between otherwise regular periods, after sex, or after menopause is considered abnormal and should be checked. It is often harmless, but it needs evaluation to rule out treatable causes.

Why are my cycles irregular after stopping birth control or nearing menopause?

Irregularity is common in the first years after periods start, in the years before menopause, and while your body re-establishes its rhythm after hormonal contraception. Still, missed periods (when not pregnant), very heavy bleeding, or lasting irregularity deserve evaluation.

Women's Health

Understanding Your Menstrual Cycle: What's Normal and What's Not

A clear, plain-language guide to menstrual cycles: normal length, flow, and duration, what counts as heavy or irregular, and when to see a clinician.

Morningside Medical Team

Reviewed by Mary Ojo-Carons, MD, Women's Health

What counts as a normal menstrual cycle

A normal cycle runs anywhere from 24 to 38 days, counting from the first day of one period to the first day of the next. Bleeding usually lasts up to about 8 days, with 2 to 7 days being typical. The famous "28-day cycle" is just an average, so yours does not have to match it to be healthy.

Key Takeaways

A normal cycle length is 24 to 38 days, not a strict 28.
A normal period lasts up to 8 days; most people bleed 2 to 7 days.
Small month-to-month variation is fine (up to about 7 days for most adults); big, unpredictable swings can signal an ovulation problem.
Heavy bleeding affects roughly 1 in 5 women and is worth treating when it disrupts your life.
Bleeding between periods, after sex, or after menopause is always worth a check.

What happens during your cycle?

Your cycle has four phases driven by hormones: the period itself (menstrual phase), the follicular phase leading up to ovulation, ovulation, and the luteal phase afterward. Four hormones (FSH, LH, estrogen, and progesterone) rise and fall to run the show.

Ovulation, when an ovary releases an egg, happens roughly 14 days before your next period starts. The phase after ovulation stays fairly fixed in length, while the phase before it varies more. That is why a longer or shorter cycle usually reflects how long it took your body to ovulate that month.

What does "regular" really mean?

Regular does not mean identical every month. A little drift is expected. For most adults (ages 26 to 41), up to 7 days of variation from one cycle to the next is normal. In the teens and in the years around 42 to 45, up to 9 days of variation is still within range.

Bigger swings than that, or cycles you simply cannot predict, can point to a problem with ovulation. That is one of the most common reasons for abnormal bleeding, and it is treatable once identified.

How much bleeding is too much?

Doctors used to define heavy periods by measuring blood loss (more than 80 mL per cycle in research settings). In real life, nobody measures that. The practical definition is blood loss heavy enough to interfere with your physical, social, or emotional quality of life.

Real-world signs your flow may be too heavy:

Soaking through a pad or tampon every hour for several hours in a row
Needing to change protection during the night
Passing clots the size of a quarter or larger
Doubling up on pads or tampons
Bleeding that keeps you from your normal activities
Feeling tired or short of breath, which can signal anemia

Heavy periods are common. They affect more than 10 million American women each year, about 1 in every 5. Common does not mean you have to live with it.

When are irregular cycles expected?

Some irregularity is a normal part of life stages. In the first years after periods begin, cycles are naturally more variable. Around the first gynecologic year, 90 percent of cycles still fall within 21 to 45 days, and longer cycles are common early on. By about three years in, 60 to 80 percent of cycles settle into the adult range of 21 to 34 days.

Cycles also tend to shift in the years before menopause, and while your body finds its own rhythm after stopping hormonal birth control. Even so, missed periods when you are not pregnant, very heavy bleeding, or irregularity that lasts still deserve a look.

When should I see a clinician?

Reach out to a clinician if you notice any of the following (CDC, FIGO):

Soaking through one or more pads or tampons every hour for several hours, or needing to change more often than every 2 hours
Changing protection during the night, or doubling up on pads or tampons
Periods lasting more than 7 to 8 days
Blood clots the size of a quarter or larger
Bleeding between periods, after sex, or any bleeding after menopause
Missed periods (when pregnancy is not the cause), or cycles consistently shorter than 24 days or longer than 38 days
Bleeding that interferes with your daily life
Fatigue, low energy, or shortness of breath, which can signal anemia

Sudden, severe heavy bleeding calls for prompt care. Tracking your cycles on a calendar or app, including start dates, length, and flow, gives your clinician a clear picture and makes any conversation easier. Our women's health team is here to help you sort out what is normal for you and what is worth treating.

Medical disclaimer

This article is for general information and is not a substitute for professional medical advice. Talk to your clinician about your specific situation.

Ready to talk about your cycle?

Whether your periods feel too heavy, too unpredictable, or just different lately, you do not have to guess. Our caring women's health clinicians can listen, run any needed tests, and help you feel like yourself again. Book an appointment with Morningside Medical today.