5 reasons why your period seems oddly light, plus when to check in with your doctor

• It's common to experience occasional changes in menstrual flow, from heavier to lighter than usual.
• Birth control, thyroid disorders, and stress can lead to a lighter period, or even a missed period.
• Call a doctor for consistently light bleeding, bleeding after sex, or pelvic pain with bleeding.

If your period seems unusually light, there may — or may not — be a reason for it. Period flow can vary from person to person, and month to month, for all kinds of reasons, most of which aren't usually a cause for concern.

Here's what experts have to say about possible causes of a light period, plus what you can do about it.

1. Pregnancy

"Early pregnancy can occasionally result in early light spotting which could be mistaken for a light period," says Alyssa Dweck, MD, INTIMINA's sexual and reproductive health expert.

"This could be simple spotting that occurs with implantation into the uterus or something more concerning such as a threatened miscarriage."

If your light period is due to pregnancy, you may have notice some telltale symptoms of early pregnancy, such as:

• Nausea
• Breast soreness or sensitivity
• Fatigue

If you experience pain in addition to these other symptoms, this could indicate a miscarriage.

Important: When bleeding is accompanied by severe abdominal or pelvic pain that feels different than your usual period cramps, head to the nearest ER. These signs may indicate an ectopic pregnancy. This potentially dangerous cause of light bleeding in early pregnancy is always a medical emergency.

2. Hormonal birth control

Lighter periods are one of the perks of hormonal birth control. This is because the hormones estrogen and progestin thin the lining of the uterus so there's less blood to shed.

"Many hormonal methods of birth control can result in light menses. For example, the hormonal types of IUDs can often lead to irregular bleeding for 3-6 months followed by a very light, but monthly, regular flow. Similarly, the low dose oral contraceptive pill will often result in a lighter shorter flow over time," says Dweck.

Other birth control methods can make your period pretty much nonexistent, like the vaginal ring, patch, or implant, which Dweck says can result in a light to almost absent flow. Changes to your period can depend on the method and how you use it. Continuous use of the pill or patch —skipping the placebo week, in other words — could lead to no period at all.

3. A thyroid disorder

"A thyroid disorder may present itself as a change in menses, including a lighter flow," says Dweck.

This hormone-producing gland in your neck is involved in several of your body's functions. When it produces too much thyroid hormone (hyperthyroidism) or too little thyroid hormone (hypothyroidism), it can cause heavy or light periods, or stop them altogether.

Note: Research suggests that hyperthyroidism is more often associated with lighter, shorter periods, while hypothyroidism is more likely to cause longer, heavier periods.

If a thyroid disorder is to blame, your light period might be accompanied by other symptoms, such as changes in weight, hair, skin and appetite, as well as temperature intolerance.

"A simple blood test can usually detect this," says Dweck.

4. Stress

Research has shown that stress, anxiety, depression, and insomnia — which are often experienced in tandem — can lead to changes in menstruation.

Your body produces more cortisol when you're under stress. This stress hormone can wreak havoc on the part of your brain that controls your period. According to the Cleveland Clinic, this can lead to delayed or light periods, or even missed periods if stress continues.

How stress affects your periods depends on how your body handles stress and how much stress you're under. The more stressed out you are, the more likely it will have a dramatic impact on your period and vice versa.

Eliminating the source of your stress or finding ways to cope with and manage it can help restore your flow.

Meditation, journaling, and taking a walk are just a few things you can do to manage stress.

If you're having trouble coping with stress on your own, connect with a mental health professional.

5. A uterine abnormality

If your periods are consistently light, this could suggest a uterine abnormality or underlying condition, according to Felice Gersh, MD, an OB-GYN and founder and director of the Integrative Medical Group of Irvine.

"Always rule out an abnormal endometrium (uterine lining cells) if light bleeding is recurrent and irregular, as it can be due to hormonal imbalance, pre-cancer and even cancer cells. This is especially important for recurrent light bleeding," says Gersh.

Gersh says that recurrent light bleeding can also indicate a polyp on the cervix or in the uterine cavity, or a fibroid within the uterine cavity. This can also happen after a surgical procedure that causes scarring of the uterine lining.

A doctor can help rule out these causes of light periods with various tests, such as a Pap smear, pelvic exam, and ultrasound.

When to connect with your doctor

A light period isn't always a cause for concern, but Gersh recommends making an appointment with a healthcare professional if:

• Pregnancy is even a remote possibility
• Your periods are consistently light or irregular
• Bleeding occurs after sexual intercourse
• Your light periods are accompanied by pelvic pain

Also consider connecting with a doctor if you experience no period at all, especially for more than three cycles — this condition is called secondary amenorrhea.

Insider's takeaway

Your period could be light for a number of reasons. While not all of these reasons pose a cause for concern, a healthcare professional can help you get to the bottom of light or irregular periods.

Reach out sooner rather than later if you notice other unusual symptoms, pain, or changes in your health.