Periods can be puzzling. Some people have two or three days of bleeding, while others see Aunt Flo for an entire week. And is it normal to have really light — or really heavy — bleeding each month?
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Ob/Gyn Erin Higgins, MD, reveals the facts about how long a period lasts and when you need to talk to your doctor.
Period length vs. menstrual cycle length
First, Dr. Higgins clarifies that period length and menstrual cycle length are not the same thing:
- Period length: Number of days you have menstrual flow (bleeding or spotting) each month.
- Menstrual cycle length: Number of days from period to period. To calculate, count from the first day of one period to the first day of the next period.
How long should a period be?
Both short and long periods can be normal — and what’s normal for you may not be normal for someone else.
“The average period length is two to seven days,” Dr. Higgins says. “Your period probably won’t be exactly the same month after month, but you should see a pattern. The length of bleeding and flow should be consistent.”
Small changes in period length are OK, but get any big changes checked out. “A little variation, like from three days to four days, is normal,” Dr. Higgins says, “but you used to have three-day periods and now they’re six days, check in with your doctor.”
Bleeding between periods
Once your period is done, you shouldn’t see spotting or flow again until your next cycle. If you’re getting bleeding or spotting between periods, call your gynecologist. Between-period spotting could be a sign of:
- Hormonal imbalances.
- Sexually transmitted infections (STIs).
- Thyroid disorders.
- Uterine fibroids (noncancerous growths in the uterus).
How heavy should a period be?
The rate of your menstrual flow depends on many factors, including the thickness of your uterine lining and hormone levels. Some people have light periods, and others have a heavy flow. Both can be normal.
“Like period length, your period flow should be somewhat predictable,” Dr. Higgins says. “If you used to have heavy periods and they become light, or vice versa, talk to your doctor.”
When periods are too heavy
There are heavy periods, and then there are heavy periods.
“Your period is heavier than normal if you soak through a pad every hour for a few hours in a row,” Dr. Higgins says. “Large clots — like the size of a golf ball or larger — are also a sign that your bleeding is too heavy.”
This type of bleeding can get in the way of your life, but don’t assume you have to suffer through it. “Your doctor can help you figure out the cause of heavy bleeding and provide treatment if needed,” Dr. Higgins says.
Hormonal birth control and periods
Your period may be shorter and lighter if you use birth control that contains hormones. The hormones in these methods are progestin alone or a combination of progestin and estrogen. Hormonal birth control includes:
- Oral contraceptive (“the pill”): These pills, which you take every day, may contain estrogen and progestin, or progestin only (also referred to as “the minipill”).
- Birth control patch: This is a sticker that you place on your skin and replace each week. It contains both estrogen and progestin.
- Vaginal ring: You place this ring-shaped device in your vagina and change it once a month. It contains both estrogen and progestin.
- Injectable contraceptive: This is a progestin-only shot that your doctor gives you every three months.
- Hormonal implant: This implant is a tiny rod-shaped device that a doctor places under the skin in your upper arm. It is effective for up to three years.
- Hormonal intrauterine device (IUD): This is a T-shaped device that your doctor places inside your uterus. It contains progestin and is effective for three to six years depending on the specific type.
Why hormonal contraceptives make periods lighter
The patch, pill and ring are designed to be used for three weeks, each with one week off. During the week off, you usually have “withdrawal bleeding,” which resembles a period. Withdrawal bleeding is a result of the sudden drop in hormones. It’s different from a true period, which comes 10 to 14 days after ovulation.
Some people take the pill, patch or ring continuously, without the hormone-free week. If you do this, you probably won’t have any bleeding at all. If you’re interested in skipping the withdrawal bleeding, ask your doctor whether continuous hormonal birth control is safe for you.
If you’re on injectable contraceptives or using a hormonal implant or IUD, your periods may be lighter, too — the result of the thinning of mucous membrane that lines the uterus.
Period length in adolescence
Preteens or teens who recently started menstruating might have unpredictable cycles and flow for a while. That’s because younger females have an immature hypothalamic-pituitary-ovarian (HPO) axis, which controls periods and menstrual cycles
“Once women reach their late teens or 20s, periods usually become more predictable,” Dr. Higgins says.
Period length and perimenopause
In the years leading up to menopause, many women experience changes in their period flow and cycle length. This time of transition is called perimenopause. It can last a year or two or several years.
If you’re in your 40s or 50s and your periods are suddenly unpredictable, perimenopause may be the reason. But play it safe and ask your doctor about any changes you notice.
Know what’s normal for you
Keep track of your periods with an app or a simple paper calendar. Take note of the rate of flow and when it shows up, so you’ll spot any changes right away.
Finally, see your gynecologist regularly and discuss your periods during your appointments. If anything seems weird to you, bring it up.
“Your period is a clue to what’s going on with your reproductive health,” Dr. Higgins says. “Your doctor wants to know the details so we can help you stay healthy.”