The blood could be coming with urine or from the vagina.
If the blood is coming from vagina then this could be due to pregnancy, ovulation bleed or implantation bleed. It all depends on the timing of spotting during your menstrual cycle. If you were expecting your periods then this could be a sign of pregnancy. So take a pregnancy test and see. If you are about two weeks from periods, then this could be ovulation bleed. You need to take a pregnancy test after 14 days to confirm pregnancy. If you are about one week from periods then this could be implantation bleed. Use of pills and depot shots do causes spotting between periods. There are many other causes of spotting between periods such as hypothyroidism, cervical dysplasia, cervical polyps, cervicitis (infection/inflammation of cervix), vaginitis (infection/inflammation of vagina), cervical and uterine cancer, uterine fibroids, hormonal imbalance as in polycystic disease of the ovary, use of blood thinners, genital ulcers, STDs and stress. A comprehensive investigation is required keeping all the points in mind.
If the blood is coming from urine then this can be due to UTI, stones, bladder polyps, infections or cysts, vaginal and cervical infections (in females), affection of kidney as in diabetes and hypertension. Please consult your PCP for primary examination followed by proper referral. Take care!