Conventional cooking methods warn about the dangers of leftover marinade. Because this liquid had contact with raw meat during the marinating process, it can contain dangerous bacteria. If you use this marinade in your cooking, you can introduce bacteria into foods, which can cause illness. If you do wish to use leftover marinade in gravy, take steps to eliminate the bacteria risk before you use the marinade in the gravy.

Place the marinade into the saucepan and set the pan onto the burner. Turn the burner to medium-high and bring the marinade to a full boil. Allow the marinade to boil for about one minute and then remove it from the heat.

Pour the pan drippings into the skillet and warm them over medium heat.

Sprinkle the flour over the drippings and stir the ingredients well to make them smooth. Cook and stir the flour and drippings for about three to four minutes until the flour browns lightly.

Slowly pour the boiled marinade into the skillet while stirring. Continue pouring and stirring until you incorporate all the marinade.

Cook and stir the gravy over medium heat until it thickens and bubbles -- about five to seven minutes.

Pour the gravy into a gravy boat to serve it.