From bright red to dark brown: What different period blood colors mean

Menstrual fluid can look different from one period to the next, one day to the next, and even one product change to the next.

Sometimes period blood is bright red, and other times it’s a dark brown discharge. It also changes in texture, meaning it might be thin and watery, thick and stringy, or it may contain clots.

“Menstrual bleeding is influenced by several factors, including hormones,” says Hilary Booth, MS, RN, WHNP-BC, a women’s health nurse practitioner with Allara. “If you are on a birth control pill, this can change how bleeding looks. If you have had a more stressful month and your ovulation was delayed, that can change how the bleeding looks.”

You may be wondering what the various shades and consistencies mean for your health. Rest assured that changes in period blood color and texture are generally normal and expected. However, sometimes changes warrant talking to a clinician, especially when accompanied by certain symptoms.

In this article, we cover what you need to know about period blood color meaning and when to talk to a doctor. Before we explore what the different colors potentially indicate, we have an important caveat. Research is scant in terms of correlating menstrual fluid colors with any particular outcome. In other words, your menstrual fluid’s appearance doesn’t serve as a metric for doctors or researchers to diagnose you with a specific concern or condition. 

Instead, clinicians rely on assessing symptoms, performing any necessary tests, and evaluating your medical history.

Why does period blood change color

Most terminology surrounding periods typically refers to menstrual fluid as blood, but the substance on your pad, tampon, menstrual cup, underwear, etc., is really a combination of three distinct bodily fluids, all of which can affect period appearance.

• Blood
• Vaginal fluid (general discharge)
• Cells and fluid from the secretory phase of the uterine endometrial lining

You may be familiar with the menstrual cycle having four phases: luteal, follicular, menstrual, and ovulatory. However, your menstrual cycle actually has two distinct but overlapping cycles: the ovarian cycle and the uterine cycle.

• Ovarian cycle: This cycle involves egg development and consists of two phases with ovulation (when the ovaries release an egg) between them.‍
  
  • Follicular phase: Begins with menstruation and continues into ovulation‍
    
  • Luteal phase: Begins during ovulation and continues until menstruation

• Uterine cycle: This cycle involves endometrium preparation and shedding (aka getting your period), with three phases:‍
  
  • Menstrual phase: Shedding of the endometrium (endometrial lining)‍
  • Proliferative phase: Regrowth of the endometrium‍
  • Secretory phase: Preparation for potential embryo implantation

While the ovarian cycle is in its follicular phase, the uterine cycle is in its menstrual and proliferative phases. Then while the ovarian cycle is in the luteal phase, the uterine cycle is in the secretory phase. Your brain sends signals to your ovaries along the hypothalamic pituitary gonadal (HPG) axis, dictating the hormonal changes in the ovarian cycle. The ovarian cycle ultimately regulates what is happening at the level of the uterus.

Factors that affect menstrual fluid color and consistency:

• Flow rate: How long blood takes to leave your body affects oxidation (a chemical reaction that occurs when blood interacts with oxygen), which can impact color.
• Hormonal fluctuations: Levels of estrogen and progesterone can affect flow volume and cycle regularity, which may affect menstrual fluid appearance.
• Underlying conditions: Uterine fibroids or polyps, infections, and more can affect menstrual fluid.
• Medications: Hormonal contraceptives and anticoagulants (blood thinners), for example, may also influence color.

What the color of your period means

Read on for the details of what the color of your period might mean. But here’s a quick reference chart.

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What does black period blood mean?

The blood present in menstrual fluid undergoes oxidation when exposed to oxygen. This means that your blood may be darker if it’s been sitting on a tampon, in your pad, in a menstrual cup, or on your underwear for a while.

It may also be darker during the early or later days of your period because of oxidation. A light flow can also contribute to more oxidation and therefore darker period blood. 

Black menstrual fluid may also result from a rare condition called hematocolpos (retained menses from an obstruction). Hematocolpos can occur from a rare pelvic tumor or when the hymen, a thin membrane covering the vaginal opening, completely blocks the opening, a condition called imperforate hymen. This prevents the flow of menstrual fluid, but period blood may eventually leak through a small opening and appear darker because of oxidation.

Additionally, endometriosis might cause darker menstrual fluid. The systemic inflammatory condition occurs when cells that mimic the endometrial lining implant outside the uterus. These implants can, in rare cases, end up on the cervix or vagina, causing irregular bleeding that may appear black or brown.

A forgotten tampon can also be the source of black menstrual fluid. Commonly, people may insert a fresh tampon without remembering to remove a previous one. Leakage from an older tampon onto the fresh one or onto your underwear may be black or a darker color.

What does brown or dark red period blood mean?

Brown or darker red period blood can also be completely normal. As mentioned above, the blood in your menstrual fluid undergoes oxidation, which can contribute to a darker shade, such as brown rather than the classic red color of, say, fresh blood emanating from a cut on your finger. Brown blood hasn’t undergone as much oxidation as black blood.

Brown blood or spotting might also be an early indicator of pregnancy from implantation bleeding. Or it could be a sign of a miscarriage or ectopic pregnancy, when a fertilized egg implants outside the uterus, typically in the fallopian tube. Both require emergency medical treatment. So if you are experiencing pain or other symptoms, seek care right away.

What does bright red period blood mean?

Bright red period blood means the blood is relatively fresh and hasn’t undergone much oxidation. You might experience bright red blood at any time during your bleed, though you might find that your menstrual fluid is darker at the start of or during the later days of your period.

What does pink period blood mean?

Pink period blood can occur from additional vaginal fluids, such as mucus or other forms of discharge, diluting the color.

Some people also have pink postcoital bleeding (bleeding after sex). This could indicate cervical polyps, cervical inflammation, a rare presentation of endometriosis found in the cervix, or even cervical cancer. If you notice this happening, you should seek an evaluation with a healthcare provider.

If you take a blood thinner medication, you may notice that you have pinkish period blood. This is because blood thinners cause a heavier flow in about 70% of people with a period. A heavier flow might be diluted with additional discharge and appear watery or pink.

What does orange period blood mean?

Orange period blood might occur if your menstrual fluid mixes with vaginal discharge; the color may be completely normal. However, it could be a sign of trouble. 

This is because a darker yellow discharge (often a sign of infection) mixing with red or brown blood may tinge your menstrual fluid orange. If you are noticing an unusual odor, itching, burning, or discomfort, talk to your provider.

What does gray or green period blood mean?

Gray or green are not normal color variations of menstrual fluid and likely indicate an underlying infection, often since increased or discolored discharge due to an infection could also discolor period blood. Potential culprits include a sexually transmitted infection (STI), such as trichomoniasis, chlamydia, or gonorrhea. However, gray or green period blood could also indicate bacterial vaginosis, which may also be an STI and require both partners to undergo treatment. 

What about clots and texture?

In addition to menstrual fluid color changes, your period may also undergo changes in texture. For example, you may experience occasional blood clots.

Your liver makes clotting factors, proteins in your blood that help form blood clots to suppress bleeding after an injury. These clotting factors can also cause your menstrual fluid to clot, especially during a heavy flow. 

Menstrual blood also contains anti-coagulant factors, which help keep the blood from getting too thick, and lytic enzymes that help break down blood clots. If your flow is fast, your body may not have enough time to thin or break down clots.

“Some clotting is normal,” Booth says. “It’s the nature of blood collecting in the uterus and sometimes the vagina. I tell my patients if you are ever passing a clot the size of the palm of your hand, that needs to be assessed, or if you notice a steady increase in the amount/size of clots you’re having with successive menstrual cycles.”

When to see a doctor

You should see a doctor if you experience any of the following:

• Extremely heavy flow: soaking through your menstrual products within one to two hours
• Excessive clotting: clots that are larger than a quarter
• Lengthy periods: lasting more than seven days
• Pelvic pain: discomfort beyond minor cramping
• Vaginal odor: foul or fishy smelling
• Vaginal or vulvar discomfort: ongoing itching or burning
• Menstrual cycle irregularity: a missed, irregular, or absent period, or a period cycle that is occurring less than 21 or longer than 35 days
• Menstrual migraine: migraine attacks that occur just before or during your period or at specific times during your cycle
• Severe premenstrual syndrome (PMS): intense mood changes or physical symptoms
• Bleeding after sex: spotting or bleeding that’s not your period after intercourse
• Unexplained vaginal bleeding: bleeding when you aren’t expecting your period

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Booth adds to see a doctor if “you notice a pattern of changes in your menstrual cycle, so three months in a row of larger/more frequent clots, change in duration of your cycle, bleeding between periods, [or] heavy bleeding requiring you to change a pad more than six times a day.”

Key takeaways

• Menstrual fluid, which is a mixture of blood, vaginal secretions, and cellular debris, can change color and texture throughout your cycle and from cycle to cycle. Generally this is normal.
• The blood in your menstrual fluid turns darker when exposed to oxygen, so a slow flow or older blood on a menstrual product generally appears darker, while fresh blood appears red.
• While most shades are normal, orange, gray, or green menstrual fluid could indicate an infection.
• If you have any concerns about your menstrual cycle, don’t hesitate to reach out to your clinician for an evaluation.

FAQ

What color period blood is concerning?

Your menstrual fluid color might change from day to day or cycle to cycle. Color changes are generally normal. However some unusual colors can be cause for concern. These include orange, gray, or green, which may indicate an infection. 

Why is my period brown on the first day?

Your period might be brown on the first day because the blood present in your menstrual fluid has been oxidized (reacted with oxygen). Remember, menstrual fluid is the shedding of your thickened uterine lining, so the menstrual fluid that first shows up as part of your period may have had more time to oxidize and therefore be darker, such as dark red, brown, or black.

What color is your period blood if you have low iron?

No medical research links period color with low iron or iron deficiency. However, many health and wellness articles try to make this connection based on the idea that iron is essential for hemoglobin, which gives blood its red color. But an iron deficiency does not suddenly make your blood pink.

Why is my period blood so dark?

Darker period blood typically just means that the blood present in your menstrual fluid has undergone oxidation, a reaction that occurs when blood is exposed to oxygen. Blood that has been on your menstrual product for a while may be darker, or the blood may have had more time to oxidize within your uterus or vagina.

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