Is the monthly lupron (leuprolide) shot an effective birth control method? if so when does it become effective?

Is effective quickly: Lupron (leuprolide) injections usually will effectively interfere with your hypothalamic-pituitary-ovarian functions, prevent ovulation and therefore reduce your risks of pregnancy. In most cases, hormonal effects probably begin promptly within a few days after the injection. Lupron (leuprolide) is not a recommended contraceptive; it is also expensive, has other indications and has some potential long term side effects.