What It Means If You Have Brown Period Blood

Sometimes during our period, the normally reddish blood takes on brown tint. Brown period blood sounds concerning, so we can't help but wonder what is going on. What is making our period blood look different? Is something weird going on?

Most often, having dark period blood is indicative of "old blood," compared to bright red active bleeding. Says Dr. Joseph B Davis DO, FACOG, “This can occur at different times of the cycle. In women who are menstruating regularly (every 25-35 days), they will often experience a variety of bleeding types.”

But having brown period blood can also be caused by many other things. It's important to consider them all and talk to your doctor.

1. Old blood

Dark blood usually occurs at the early and/or the final days of the period. “Blood from the lining will coagulate in the uterus or vagina and change from red to brown before coming out when the period is starting or finishing,” Dr. Davis says.

For some women, brown period blood happens frequently at the end of the menstrual cycle, which is perfectly normal if it lasts for only a few days.

2. Increase in iron

"Brown blood can always be caused due to an increase in iron," advises Lindsay Wynn, founder of wellness brand Momotaro Apotheca. "The presence of iron will also increase the likelihood of oxidization."

3. Isthmocele

“Women who have had Caesarean sections can have something called isthmocele, which is a lower uterine scar that collects menstrual blood and can cause dark brown flow throughout the month,” Mark P. Trolice, M.D., board-certified OB/GYN and reproductive endocrinologist, says.

Although this condition is harmless, an isthmocele can be bothersome due to the continued vaginal discharge. As Dr. Trolice warns, “It also can increase the risk for infertility by collecting fluid in the upper part of the uterus, which interferes with embryo implantation.”

4. Hydrosalpinx

This is the medical term for a blocked, swollen, fluid-filled fallopian tube, which usually results from a prior pelvic infection.

“This condition can also cause dark brown flow throughout the month. For infertility patients, surgery is required to open or remove the damaged fallopian tube. In cases where the woman is experiencing pain from the blockage, the tube is typically surgically removed,” says Dr. Trolice.

5. Birth control

Having dark period blood can also occur throughout the cycle, and is seen often when on birth control.

According to Dr. Davis, “There are two types of birth control pills: those with estrogen and progesterone, and those with only progesterone hormone. If you are on a progesterone only pill, the lack of extra estrogen means your uterine lining may be abnormal, and this can cause irregular 'breakthrough bleeding', which is often brown.”

6. Possible miscarriage

For pregnant women, brown blood from the vagina can be a sign of a threatened miscarriage.

“In the first trimester, up to one-third of pregnant women experience bleeding that ranges from bright red blood to brown,” warns Dr. Trolice. “Of these women, up to 50 percent may experience a complete miscarriage. Any bleeding during pregnancy, particularly associated with pain, should prompt you to notify your OB/GYN right away.”

7. Uterine polyps and inflammation

“Polyps are an over-growth of the lining of the uterus and can bleed sometimes. This blood is light and can be either red or brown,” Dr. Davis advises.

8. Endometriosis

“Chronic Endometritis is a condition of uterus lining inflammation which can also cause brown blood,” says Dr. Davis.

Aly Walansky is a NY-based lifestyles writer who focuses on health, wellness, and relationships. Her work appears in dozens of digital and print publications regularly. Visit her on Twitter or email her at alywalansky@gmail.com.