Carrie I was reading up on the injections and the current thoughts are that the blood levels of progesterone do not relate to the uterine level of progesterone. Studies recently have found that the progesterone absorbed through the cervix wall does something special in the way it is absorbed (technical term I forget off the top of my head) that maintains the local level of progesterone in the uterus. I think it said that to get the same level of response you would have a whooping hugmungous dose by injection to achieve a similar result.. If you want I can dig out the info for you.