Why is My Period Blood Black? Understanding the Underlying Health Facts

Introduction

Menstruation is a natural process that every woman experiences. It involves the shedding of the uterus lining with blood exiting through the vagina. Period blood varies in colour, ranging from bright red to dark brown, or even black in some cases, depending on factors such as flow and the length of time that the blood remains in the uterus. Black discharge may seem alarming, but it is often harmless and just a result of old blood taking longer to exit the body.  

In this article, we’ll look at why it occurs, as well as what other colours of period blood can mean for your health. We’ll also discuss when you should be concerned and ask a doctor for advice.   

Normal Period Blood Colour Spectrum

Colour changes during a period can be normal. They can tie back to factors like hormone changes and health issues specific to you.  

1. Black-coloured Period Blood

Period blood that is black often means old blood. This is because slower flow delays its exit from the uterus and exposure to air oxidises it giving a darker colour. You might see this colour at the start or end of a menstrual cycle. However, it can also happen after pregnancy or signal issues like infections or retained menses. Importantly, dark coloured discharge may be a sign of miscarriages, along with abdominal cramps or pain¹. If you see black-coloured period blood for the first time and feel worried, check with your healthcare provider.  

2. Brown or Dark Red coloured Period Blood

Brown or dark red period blood often shows up at the start or end of a period. It’s normal. The colour is a sign of older blood exiting from uterus lining which is deeper. It had more time to get oxidized. Other causes of brown or dark red period blood can be early pregnancy, miscarriage, or postpartum bleeding (lochia).  

3. Bright Red coloured Period Blood

Bright red period blood shows fresh blood leaving the uterus quickly. It usually shows up at the start of a period². You might see the bright red colour all through your period or you might see the colour changing to darker tones as the flow slows down. Bleeding between the periods or abnormal bleeding could indicate hormonal imbalance, infections, or early pregnancy and evaluation is advised in such cases.  

4. Pink-coloured Period Blood

This occurs when your blood and cervical mucus mix together. You typically find this during light bleeding at the start or end of a menstrual cycle². Spotting between periods or light blood flow could also turn your period blood pink. A huge weight loss, poor diet, or anaemia can also cause pink blood.  

5. Orange coloured Period Blood

Just like pink-coloured period blood, orange-coloured period blood happens when blood mixes with cervical fluid. It may also be associated with hormonal fluctuations due to contraception or ovulation spotting. Yet, an orange discharge might suggest an infection, perhaps bacterial vaginosis or trichomoniasis. An itchy feeling, pain, and bad smell down may be associated symptoms. Reach out to a healthcare professional for a check-up when you notice these symptoms.  

6. Grey coloured Period Blood

Greyish discharge is abnormal and strongly associated with an infection, commonly bacterial vaginosis³. You might have itching, a foul smell, and discomfort in the vaginal area. It may also occur in miscarriage. If you see grey period blood, consult with a healthcare provider. You’ll need management to avoid complications.  

Figuring out these changes helps to calm fears and understand that the colour of your period blood is not always a bad sign. 

Common Causes of Black-Coloured Period Blood

The reasons for black-coloured period blood are described below.   

1. Beginning or End of Your Period

Black discharge at the start or end of your period often means old blood. That points to a slow flow. It’s normal and not a concern unless other worrying symptoms show up.  

2. Stuck or Forgotten Object

Something stuck in the vagina like a tampon, condom, or contraceptive device can cause irritation. That may lead to black discharge. Infections due to leaving a foreign object in the vagina might cause more symptoms. You might smell something foul, feel itchy, get a fever, have pain in the pelvis, or find it hard to pee. This is a medical emergency and requires prompt removal⁴. 

3. Infection

PID (pelvic inflammatory disease), gonorrhoea, and chlamydia infections can lead to black discharge during your period. These infections could make vaginal discharge heavier and change its colour. You might also have a foul smell, feel itchy, have a burning sensation or pain in your pelvis.  

(PID is an infection of female reproductive parts like the uterus, fallopian tubes, or ovaries. It can come from sexually and non-sexually transmitted infections. It can cause minor or major pain in the lower abdomen, among other symptoms⁵.) 

4. Missed Miscarriage

A missed miscarriage happens when the embryo stops growing, yet, it doesn’t leave the body for many weeks. This is diagnosed on an ultrasound but black spotting or discharge can show up in these cases. You might also see a loss of pregnancy signs, cramping, or vaginal discharge of fluid or tissue¹.  

5. Lochia

Lochia is what we call bleeding after childbirth. It can last up to six weeks. Slow blood flow during lochia can turn it dark brown or black. The dark discharge last for a few days to couple of weeks and with time, the colour starts fading before it stops entirely⁶.  

6. Retained Menses

Retained menses, or hematocolpos/hematometra, happens when menstrual blood collects in the vaginal cavity. The kept blood turns darker, leading to black discharge. Retained menses can come from birth defects affecting the hymen, vaginal septum, or cervix.  

The Role of Hormones and Menstrual Cycle

Health issues tied to hormones can change the colour and feel of period blood. This is especially so during a normal menstrual cycle.   

• Polycystic Ovarian Syndrome (PCOS): PCOS is a condition impacting hormone levels in women. It messes with the balance between oestrogen, progesterone, and testosterone. PCOS can cause infrequent or delayed periods, leading to oxidized, darker blood due to prolonged endometrial buildup. Other symptoms include excess hair growth, weight gain, and acne⁷. 
• Perimenopause: It’s the stage before menopause. Changes in oestrogen levels during this time cause changes in menstrual cycles. Brown or dark red coloured period blood can result from these hormone changes. You might also get heavier or lighter periods, more spotting, or cycles shorter or longer than normal. If bleeding becomes erratic or unusually heavy during perimenopause, evaluation for polyps or hyperplasia is important. 
• Low Oestrogen: Low oestrogen levels can also influence the colour and feel of period blood⁸. Sometimes, this can cause black or pink-coloured discharge. While low oestrogen itself leads to lighter bleeding or spotting, black discharge here is more often due to delayed outflow. Common reasons for low oestrogen levels include menopause, lots of exercise, or certain hormonal birth control methods, such as an IUD. 

When to Be Concerned About Black-Coloured Period Blood?

Though black-coloured period blood is often not a concern, it’s crucial to keep your eyes open for signs of danger which are described below.   

1. Infections and Their Symptoms

Infections like PID or STIs like trichomoniasis, gonorrhoea, chlamydia can lead to black-coloured period blood. They may also cause a foul-smelling discharge, pain, or itchiness in the vaginal area. If you have the above symptoms always consult with a healthcare professional for a proper check-up and management.  

2. Uterine Polyps, Fibroids, and Adenomyosis

Uterine growths like polyps or fibroids, and adenomyosis (a condition where the uterine lining grows into the muscular wall), can lead to black coloured period blood or clots. These can cause prolonged or heavy bleeding, clots, and dark discharge due to inefficient uterine contractions Heavy, non-stop bleeding may point towards these conditions and require a consultation with a healthcare provider⁹. 

3. Persistent Black Blood Clots

Persistent black discharge during your period, mainly if there’s severe pain or heavy bleeding, may be a sign of a health issue. A healthcare professional can do a thorough check-up and discuss management options.  

4. Signs It Might Be Cervical Cancer

Although rare, persistent black discharge and altered bleeding patterns could point to cervical cancer. Pain in the pelvis, pain during sexual intercourse, and post-coital bleeding are more symptoms. Unusual vaginal bleeding or dark discharge outside of periods, especially post-menopause, may warrant cervical cancer screening. If you observe these symptoms, call a healthcare professional for a proper check-up¹⁰.  

Non-Cancerous Myths and Misconceptions

Many myths surround the topic of black-coloured period blood. Knowing the truth from lies helps give both comfort and sound health advice.  

• Black Coloured Period Blood and Infertility: Just seeing black coloured period blood often doesn’t mean you’re infertile. Yet, certain conditions, such as PID or PCOS, can lead to black coloured period blood and affect fertility. A healthcare provider can provide a full understanding based on your unique situation.  
• Black Coloured Period Blood on Birth Control: Some women might see black-coloured period blood or strange bleeding patterns while on hormonal birth control, like an IUD. This doesn’t always mean trouble. But if you’re worried about your period blood colour or other symptoms, discuss with your healthcare provider for advice.  

Remember that colour alone is not diagnostic. It must be correlated with symptoms and clinical context. 

When to Consult a Doctor?

Turn to a doctor for strange symptoms along with black-coloured period blood. This could be lasting pain, a foul smell, or fever. Also, seek medical help if you bleed during pregnancy or after menopause, or see black discharge or unexpected bleeding.  

Symptoms That Require Immediate Medical Attention

Watch out for these signs that call for immediate medical help.   

• Heavy bleeding that needs you to change pads or tampons often  
• Large sized blood clots  
• Severe pain during your period  
• Fever and feeling sick after using a tampon (a possible sign of toxic shock syndrome)  
• Any bleeding or spotting if you’re pregnant  
• Bleeding after intercourse 
• Bleeding lasting more than 7 days 
• Cycles shorter than 21 days or longer than 35 days 

Conclusion

Knowing the many colours of period blood and their meanings is vital for your reproductive health. Black-coloured period blood might look scary, but it’s often the result of oxidized old blood. It does not usually signal danger. Even so, if black period blood comes with other symptoms, or occurs during pregnancy or post-menopause, you must discuss it with a healthcare professional for a proper check-up and guidance.  

Frequently Asked Questions (FAQs)

References

1. Medline Plus. Miscarriage. [Internet]. [cited 2025 Aug 8]. Available from:  https://medlineplus.gov/miscarriage.html
2. Habiba M, Benagiano G. The Duration of Menstrual Blood Loss: Historical to Current Understanding. Reproductive Medicine. 2023; 4(3):145-165. https://doi.org/10.3390/reprodmed4030015  
3. Kairys N, Carlson K, Garg M. Bacterial Vaginosis. [Updated 2024 May 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459216/ 
4. National Center for Biotechnology Information (NCBI). Vaginal Foreign Body Evaluation and Treatment [Internet]. [cited 2025 Aug 8]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549794  
5. Centers for Disease Control and Prevention (CDC). Pelvic Inflammatory Disease (PID) – CDC Basic Fact Sheet [Internet]. [cited 2025 Aug 8]. Available from: https://www.cdc.gov/pid/about/index.html 
6. Blood loss – what to expect after the birth of your baby. University Hospital Southampton [Internet]. [cited 2025 Aug 8]. Available from: https://www.uhs.nhs.uk/Media/UHS-website-2019/Patientinformation/Pregnancyandbirth/Blood-loss-what-to-expect-after-the-birth-of-your-baby-743a-PIL.pdf  
7. PCOD National Health Service (NHS). Overview – Polycystic ovary syndrome [Internet]. [cited 2025 Aug 8]. Available from: https://www.nhs.uk/conditions/polycystic-ovary-syndrome-pcos  
8. Xiping L, Xiaqiu WU, Lirong B, Jin P, Hui KK. Menstrual cycle characteristics as an indicator of fertility outcomes: evidence from prospective birth cohort study in China. J Tradit Chin Med. 2022;42(2):272-278. https://pmc.ncbi.nlm.nih.gov/articles/PMC9924698/ 
9. National Center for Biotechnology Information (NCBI). Uterine Fibroids (Leiomyomata) and Heavy Menstrual Bleeding – PMC [Internet]. [cited 2025 Aug 8]. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9580818  
10. American Cancer Society. Signs and Symptoms of Cervical Cancer [Internet]. [cited 2025 Aug 8]. Available from: https://www.cancer.org/cancer/types/cervical-cancer/detection-diagnosis-staging/signs-symptoms.html  

Disclaimer: The information provided here is for educational/awareness purposes only and is not intended to be a substitute for medical treatment by a healthcare professional and should not be relied upon to diagnose or treat any medical condition. The reader should consult a registered medical practitioner to determine the appropriateness of the information and before consuming any medication. PharmEasy does not provide any guarantee or warranty (express or implied) regarding the accuracy, adequacy, completeness, legality, reliability or usefulness of the information; and disclaims any liability arising thereof. 

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