Menstruation (commonly known as vacation) day 1 blood like mixed with water means that the color of menstrual blood is light, such as no accompanying abdominal pain and other abnormal symptoms, can be temporarily observed without special treatment. If the color of menstrual blood is light for a long time and other abnormal symptoms appear, consider diseases, such as uterine or ovarian diseases or anemia and other factors: 1. Endometrial hyperplasia: due to various factors, resulting in high levels of estrogen in the body, long-term stimulation of the endometrium, and there is not enough progesterone to counteract it, easily lead to abnormal endometrial hyperplasia. This may manifest as irregularities in the menstrual cycle, duration, and bleeding volume, and may be accompanied by abnormal vaginal discharge during menstruation, resulting in blood on the first day that looks like it has been mixed with water and is light in color. For patients with endometrial simple hyperplasia and complex hyperplasia, clinical treatment is mostly performed with kynurenine tablets or amnestic progesterone. For patients with atypical endometrial hyperplasia who require preservation of reproductive function, clinical treatment is mostly carried out with medroxyprogesterone acetate tablets or medroxyprogesterone acetate tablets. If drug treatment is ineffective, or for patients with atypical endometrial hyperplasia but no fertility requirements, total hysterectomy can be performed according to medical advice. 2. Decline in ovarian function: Due to factors such as aging and ovarian diseases, the ovarian function declines and hormone secretion is abnormal, which can lead to a decrease in menstrual cycle and menstrual volume, making the first day of menstrual blood lighter in color and like water adulteration. Patients of childbearing age can temporarily not take drugs, if the decline is serious, oral hormone replacement drugs can be prescribed to help women maintain normal menstruation every month; 3. Anemia: Due to the decrease in the volume of human peripheral blood red blood cells, it is easy to produce symptoms such as fatigue and dizziness, while women of childbearing age can experience a decrease in menstrual volume, which subsequently causes the color of menstrual blood to become lighter, like mixed with water. The causes of anemia are different and so is the treatment. For example, iron deficiency anemia should be promptly supplemented with iron, while the primary cause of iron deficiency should be actively treated, while megaloblastic anemia should be supplemented with folic acid or vitamin B12 to improve symptoms. 4. Endometrial inflammation: Inflammation occurs when the endometrium is infected with pathogens, and inflammatory stimulation can result in abnormal vaginal secretions, which dilute menstrual blood like water, and can be accompanied by lower abdominal pain. Usually the corresponding sensitive antibiotic treatment needs to be given according to the infecting pathogen, and sometimes broad-spectrum antibiotics or combination of drugs such as cephalosporin, metronidazole, penicillin, etc. can be chosen.