When you use injectable contraceptives you may have bleeding and spotting between periods. The menstrual bleeding may vary from slight staining between menstrual periods to breakthrough bleeding, which is a flow much like a regular period. It occurs most often during the first few months of usage, but may also occur after you have been using the injectable contraceptive for some time. Such bleeding may be temporary and usually does not indicate any serious problems. It is important to continue using the injections on schedule. If the irregular bleeding or spotting is heavy or lasts for more than a few days, you should consult your doctor or healthcare provider.