GET A NEAR-INFRARED SAUNA
I use one from Saunaspace.com
It will revitalize his body and restart the ATP process, which is vital. Also try Reishi mushroom (available in health food stores or AMZ) which is an immunomodulator (it boosts your immune system)
He may have a virus in which case Oregano Oil and other natural supplements can be applied. Educate yourself and you can save him. Doctors will not tell you about medicinal mushrooms but they are key–there's a whole lot of them that do different things to cure diseases. research Paul Stamets he is the pioneer