Why Is Menstrual Blood Black on the First Day of the Period?

A woman’s menstrual blood should normally be bright red. On the first day of menstruation, the flow is typically light, and the period usually lasts 3–5 days. However, an increasing number of women are experiencing menstrual irregularities, including changes in menstrual blood color. Some women notice dark or black blood on the first day of their period—a phenomenon that causes significant concern. So, what causes black menstrual blood on the first day of menstruation? Below, we address this question.

Why Is Menstrual Blood Black on the First Day?

1. Kidney Deficiency: Menstrual blood appears dark or black, often accompanied by an irregular cycle—periods may occur earlier or later than expected—and scanty flow. The blood color is pale red or dull red, and its consistency is thin. Symptoms include soreness and weakness in the lower back and legs, heel pain, dizziness, tinnitus, and a sensation of coldness in the abdomen.

2. Cold in the Blood: Menstrual blood appears dark or black, with delayed periods and reduced flow. The blood is dark in color, and the lower abdomen feels cold and painful. Warming the lower abdomen provides relief. The tongue coating is white, and the pulse is deep and tight. Treatment focuses on warming the meridians and dispelling cold.

3. Deficiency of Both Qi and Blood: Menstrual blood appears dark or black, and the cycle becomes irregular—periods may occur earlier or later than usual. Menstrual flow may increase or decrease, and the duration of menstruation may lengthen. The blood is pale in color and thin in consistency. Mild abdominal pain may occur, along with fatigue, spontaneous sweating, pallor or sallow complexion, poor appetite, anorexia, and constipation. The tongue is pale red, and the pulse is fine and weak. Treatment aims to tonify qi and nourish blood.

4. Qi Stagnation and Blood Stasis: Menstrual blood appears dark or black, with unpredictable timing (early or late), variable flow (heavy or light), and dark purple-red blood containing clots. Menstruation may be sluggish or obstructed. Additional symptoms may include lower abdominal pain exacerbated by pressure, distending pain in the chest, ribs, breasts, or lower abdomen, epigastric fullness and discomfort, a purplish-dark tongue or one with petechiae, a thin white or thin yellow tongue coating, and a wiry or choppy pulse. Treatment focuses on activating blood circulation, resolving stasis, regulating qi, and relieving pain.

The above outlines the primary causes of black menstrual blood on the first day of menstruation. We hope this information is helpful to you.