Why is the first day of menstruation black? Uncovering the scientific reasons for the color of menstrual blood
Menstruation is a barometer of women's health, and changes in the color of menstrual blood often cause concern. Especially when black or dark brown blood appears on the first day of menstruation, many women feel confused and even worried. This article will combine the hot health topics on the Internet in the past 10 days to scientifically explain this phenomenon and provide relevant data analysis.
1. Top 5 hot topics on women’s health in the past 10 days on the Internet

| Ranking | topic | Search volume (10,000) | Main discussion points |
|---|---|---|---|
| 1 | Abnormal color of menstrual blood | 128.6 | Causes of black/brown menstrual blood |
| 2 | Period headache relief | 95.3 | Natural remedies and medication options |
| 3 | Contraceptive methods comparison | 87.1 | Side effects of new birth control methods |
| 4 | polycystic ovary syndrome | 76.8 | Early symptom recognition |
| 5 | Menstrual mood management | 62.4 | Hormone fluctuations linked to mood |
2. The scientific explanation for the black color on the first day of menstruation
1.Caused by oxidation reaction: After the endometrium is shed, if the menstrual blood stays in the uterine cavity for a long time, the iron in the hemoglobin will react with oxygen, causing the bright red blood to gradually turn into dark brown or even black.
2.old bleeding: A small amount of menstrual blood that was not completely discharged during the previous menstrual cycle may be discharged first at the beginning of the new cycle. This "inventory" blood will become darker in color due to longer storage time.
3.changes in hormone levels: The progesterone level drops rapidly at the beginning of menstruation, which may cause the shedding of the endometrium to slow down and the blood to be partially oxidized before being discharged.
3. Health signals corresponding to different menstrual blood colors
| color | Common occurrence times | Possible reasons | Do you need medical attention? |
|---|---|---|---|
| dark black/brown | Cycle Days 1-2 | Oxidation of old blood | Usually not required |
| bright red | Cycle Days 2-4 | fresh bleeding | normal phenomenon |
| orange red | any time | possible signs of infection | Recommended to check |
| gray red | any time | bacterial vaginosis | Need treatment |
| pink | The beginning and end of the cycle | Less menstrual flow | Pay attention to anemia |
4. Abnormal situations that require vigilance
1.with severe pain: If black menstrual blood is accompanied by severe menstrual cramps, it may indicate endometriosis or adenomyosis.
2.Lasts too long: If you continue to discharge black menstrual blood for more than 3 days, it is recommended to undergo a gynecological examination.
3.Abnormal smell: If there is an obvious stench, there may be an infection that needs treatment.
4.Appears outside menstruation: If black discharge occurs between menstruation, organic diseases need to be investigated.
5. Lifestyle suggestions for improving the color of menstrual blood
1.moderate exercise: Regular aerobic exercise can promote pelvic blood circulation and help menstrual blood to be discharged smoothly.
2.Belly warmth: Using a hot water bottle or hot compress can relieve uterine contractions and reduce menstrual blood retention.
3.Supplement iron: Appropriate intake of iron-rich foods such as animal liver and red meat can improve blood quality.
4.Well hydrated: Drink 1500-2000ml warm water every day to dilute blood concentration.
6. Expert opinions and latest research
According to the latest research in the "International Journal of Obstetrics and Gynecology" in 2023, about 78% of healthy women occasionally experience black menstrual blood on the first day, which is directly related to the frequency of uterine contractions and the speed of menstrual blood discharge. Gynecologists emphasize that simple color changes without other symptoms are usually normal physiological phenomena.
It is worth noting that the recent hot discussion on social media about the "menstrual blood color detoxification theory" lacks scientific basis. The color of menstrual blood mainly reflects the length of time the blood remains in the body, rather than the so-called "toxin" content.
From the above analysis, it can be seen that the appearance of black blood on the first day of menstruation is normal in most cases. Female friends should view this physiological change rationally and learn to recognize warning signs that truly require medical treatment, without being overly anxious or ignoring possible health problems.
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