Hi Dark brown flow during menstruation may not be a cause for concern.It is mostly because blood stays longer in you before exiting the body.When blood stays for log, it turn dark and at times brown.End of cycle blood flow can also be dark.What you should observe should be the odor, if it smells, it may indicate an infection to investigate. Scanty blood flow may not also be pathologic,however, some common causes are: -Use of hormonal contraceptives and intrauterine device -Polycystic ovarian disease -Genetic factors I will advise you just observe for other pelvic signs like pelvic pain and funny discharges.If none of these, just stay calm till your next menses.If the problems repeats, the you get a pelvic ultrasound for investigation and see a Gynecologist for evaluation. Hope my answer will help you Best regards