Most women bleed for about 5 days during a period. Normal periods vary greatly from woman to woman. Normal flow ranges from about 2 tablespoons to as much as one cup (240 cc) of blood per day. Normally, the amount of blood loss is not dangerous to your health.

Common causes for irregular menstrual periods include:

• Anxiety disorders
• Birth control pills
• Bleeding from anticoagulant
• Cervical polyps
• Cervicitis
• Diabetes
• Drug side effects:
• Medication side effect causing heavy menstrual bleeding
• Dysfunctional uterine bleeding
• Hormone abnormalities
• Hypertension
• Infection:
• Endometritis
• Pelvic inflammatory disease
• Intrauterine device
• IUD
• Kidney disease
• Liver disease
• Miscarriage
• Obesity
• Ovarian cystic disease
• Puberty
• Uterine fibroids

Less common causes for irregular menstrual periods include:

• Adrenal and pituitary gland disease
• Bleeding disorders
• Bleeding disorders
• Ectopic pregnancy
• Factor 10 deficiency
• Factor 2 deficiency
• Factor 5 deficiency
• Factor 7 deficiency
• Hyperthyroidism
• Hypothyroidism
• Liver disease
• Ovarian cancer
• Platelet function disorder
• Polycystic ovary disease
• Uterine cancer
• Vaginal tumors
• Von Willebrand's disease