As reported in an excellent review1 on the “recent progress toward hydrogen medicine,” the author describes various methods being used in published animal and human studies to administer hydrogen: inhalation of hydrogen gas, oral ingestion by drinking hydrogen water, hydrogen baths (because hydrogen easily penetrates the skin and distributes throughout the body via blood flow),1 injection of hydrogen saline, direct absorption of hydrogen (as in hydrogen containing eye drops), and INCREASED PRODUCTION OF HYDROGEN BY GUT BACTERIA. Note: One reason for the use of hydrogen water and hydrogen saline is that it is possible to reliably control the dose administered to experimental animals, which is important in determining results such as dose-response relationships. In the case of gut bacteria-provided hydrogen, it is less easy to determine the hydrogen “dose,” although one way to at least partially overcome this problem is to measure the hydrogen gas excreted by the lungs...
http://www.life-enhancement.com/magazine/article/2642-hydrogen-therapy