Can I take a medication to reduce my blood pressure in order to safely take methylergonovine?

No. Merthergonovine (methergin) is not a safe medication for patients with hypertension. There are other safer alternatives. I would not advise taking blood pressure medicine simply to be able to use this drug. Your blood pressure needs to be treated, and then I would recommend using a different medication like Misoprostol for postpartum bleeding.