Hi! I appreciate your concern. Since you are intending to use hCG injection to reduce your body weight, this is not a genuine clinical use of the drug. It is called as misuse of drug to decrease the body weight and enhance the performance. Since the weight you have gained is due to Prednisone and the fact that you are gradually tapering the dose, in due course of time you weight will also decrease. I am of the opinion that you should not take Inj hCG just to get rid of the excess of body weight. You can try other measures like life style modification such as regular physical exercise, eat healthy diet, avoid fast.junk foods, reduce the dietary salt intake, take plenty of water. Use of hCG has adverse impact on your health. Methotrexate as such has no interaction with hCG injection. Take care of your health.