Periods vary from person to person and even month to month! Still it’s reassuring to know whether your period experience falls in the “normal” zone.

An average period is about 2 to 3 tablespoons of blood. Periods are considered regular if they happen every 24 to 38 days.

It’s considered unusual or abnormal if your period is different from what’s typical for you. Signs of a light period are:

  • bleeding less than you normally do or less than the average 2 to 3 tablespoons
  • flow is light enough for a panty liner, or fewer pads and tampons than usual
  • “spotting” (only a little blood in your underwear or when you wipe) instead of a real flow
  • light bleeding at a time that you aren’t expecting your period

Whether your period has suddenly faded or you’ve always had a low flow, there are lots of factors that can contribute to light periods. Here are 14 causes to look out for.

Periods and pregnancy: An odd couple

You might be pregnant if you experience these symptoms:

  • extreme tiredness
  • tender, swollen breasts
  • upset stomach with or without throwing up (morning sickness)
  • cravings or distaste for certain foods
  • mood swings
  • constipation
  • frequent urination
  • headache
  • heartburn
  • weight gain or loss

It can be pretty confusing if you have those pregnancy signs and a little bit of bleeding.

If you’re pregnant, the bleeding isn’t actually a period. It may be implantation bleeding. When a fertilized egg implants in the uterine wall, slight bleeding and cramping can occur.

If you suspect pregnancy and your regular period is a no-show, take a home pregnancy test. If it’s negative but you still have weird symptoms and no flow, test again or follow up with your doctor.

Don’t expect regular periods during breastfeeding

While a woman breastfeeds, her body produces a hormone called prolactin.

Prolactin suppresses ovulation and periods for several months or up to a year after childbirth. When periods do return, they may be irregular and shorter or lighter than you are used to, as long as you’re still breastfeeding.

Don’t count on breastfeeding for birth control though! You can still ovulate and get pregnant, but it’s even harder to predict the timing.

Weight changes and extreme dieting screw up periods too

Losing weight to the point of a very low body fat percentage will stop ovulation and periods. This is particularly a problem with women living with anorexia nervosa.

Research has also shown that binge eating is associated with changes in period flow.

Lest you think only very thin women with eating disorders have to worry about lighter or absent periods, it seems dieting can mess up periods for people of every size.

A 2016 study found that dieting behaviors are associated with menstrual disruption, regardless of body mass index and eating disorder diagnosis.

Consider skipping the diet and finding a nutrition professional who practices Health at Every Size (HAES).

If you think your light periods are due to not eating enough, let a doctor evaluate your overall health and contact a mental health professional to discuss eating disorders.

Like sands through the hourglass, so are the periods of our lives

Periods typically get lighter as a woman ages. They may be heavier in teen years and get lighter in your 20s and 30s. In their 40s, most women enter perimenopause and have shorter or lighter periods.

During perimenopause, ovaries produce less estrogen and progesterone, and ovulation is less frequent. Lack of ovulation is a common underlying factor for light or absent periods. Other signs of perimenopause include:

  • irregular periods
  • hot flashes
  • vaginal dryness
  • sleep problems
  • mood changes
  • bone loss
  • forgetfulness

Birth control is also period control

Birth control pills prevent ovulation with a daily dose of estrogen and progestin. No ovulation means no period. During the week of placebo pills (containing no hormones) a woman experiences breakthrough bleeding while the uterine lining sheds.

Because hormonal methods of birth control (the pill, the patch, the ring) don’t let the uterine lining build up as much, periods are lighter. These are some other side effects of hormonal birth control:

  • nausea
  • weight gain
  • sore breasts
  • mood changes
  • spotting between periods

Lighter periods are nothing to worry about when you’re on the pill, unless you suspect you’re pregnant.

Stress is bad news

Living with stress impacts all aspects of mental and physical health. Is it any surprise it also impacts the menstrual cycle?

A 2018 study of stress and menstrual problems in health science students found a correlation between how stressed the women felt and their experience of abnormal bleeding and irregular periods.

Stress may also cause functional hypothalamic amenorrhea (FHA), affecting about 17.4 million women worldwide. FHA disrupts interaction between the hypothalamus, pituitary gland, and ovaries.

Suppression of several hormones in this system leads to low estrogen levels and prevents thickening of the uterine lining. FHA may produce no bothersome symptoms beyond stopping periods, but the hormone disruption can cause long term problems.

Try these techniques to reduce stress:

  • get regular exercise
  • drink less caffeine
  • make social connections
  • set boundaries and make fewer commitments
  • start a mindfulness practice

Exercise, but not too much

When women spend more energy exercising than they take in through diet, reproductive, bone, and cardiovascular health can suffer.

This phenomenon has been recognized in participants of sports that emphasize smaller body size, lean body composition, and endurance (think ballet, long distance running, gymnastics, and swimming).

Not just elite athletes are at risk, though. Any woman who significantly increases her energy expenditure can notice menstrual changes such as lighter periods.

Here are other signs you might be overexercising:

  • feeling more tired than usual
  • depression, anxiety, or irritability
  • sore muscles
  • overuse injuries
  • vulnerability to contagions
  • weight loss

If symptoms don’t improve after a few weeks of rest, see a doctor.

PCOS is a pain in the PCO-ass

Polycystic ovary syndrome (PCOS) affects 5 to 10 percent of women of reproductive age.

Because it’s associated with reproductive hormonal imbalance, periods with PCOS can be all over the place: light, heavy, long, short, irregular, or absent.

PCOS is named for the bumpy cysts covering the ovaries. Those cysts contain eggs that weren’t released due to hormonal imbalance. High levels of androgens (reproductive hormones that are usually higher in males) prevent ovulation.

If you have a history of unpredictable periods along with these other symptoms, ask your doctor about PCOS:

  • excess hair on the face and other body parts
  • acne on the face, chest, or back
  • scalp hair loss or thinning
  • weight gain
  • darkening of skin around the neck, groin, arm pits, and under breasts
  • skin tags

Symptoms of PCOS can be treated with hormonal birth control, insulin-sensitizing drugs, and anti-androgens.

Other medical culprits for light periods

These other conditions can also cause period irregularities:

  • Primary ovarian insufficiency. When a woman’s ovaries stop functioning before the age of 40.
  • Thyroid dysfunction. Producing too much or too little of the hormones that regulates metabolism.
  • Uncontrolled diabetes. Dysfunction of the body’s ability to use glucose in the blood.
  • Cushing’s syndrome. An illness caused by overproduction of cortisol.
  • Congenital adrenal hyperplasia. A rare genetic condition affecting the adrenal glands.
  • Uterine scarring. Caused by intrauterine procedures, surgery, or inflammation.

Anyone can experience menstrual changes due to these and other causes. These factors make it more likely to happen:

  • pregnancy and breastfeeding
  • weight changes and disordered eating
  • high stress
  • approaching menopause age (usually early 50s)
  • people with conditions that cause hormone abnormalities, like PCOS

It’s a good idea to see the doctor any time you experience unusual vaginal bleeding, including:

  • bleeding after sex
  • spotting or bleeding when it’s not time for your period
  • a period that is heavier or longer than normal
  • bleeding after menopause

If more serious concerns are ruled out, the doctor may prescribe hormonal birth control to regulate your periods.

A light period is usually not a sign of a very serious condition, but it never hurts to know what’s causing changes in your cycle. If you experience any unusual (for you) vaginal bleeding, make note of other symptoms to share with a healthcare provider.

Many causes are temporary, treatable, or manageable. It also helps to know what to expect from periods when you’re expecting, when you’re breastfeeding, and when you’re aging into a magnificent menopausal club of wise women.