Vitamin C IV dosing is not about the body "absorbing" it. Its about raising the concentration of vitamin C in the blood. Other animals can produce their own vitamin C and saturate their blood with it, which is why animals such as bats are able to remain healthy despite being exposed to lots of different viruses. Vitamin C is literally a sterilizing agent against viruses. When its present in the blood in high concentration, it kills any viruses it comes in contact with while not affecting any cells or tissues. That is the point. This crap about absorption is a clear sign of a fundamental misunderstanding of how this shit actually works. Its also why oral intake of vitamin C is not effective and you need to administer it directly into the blood, because if taken orally it first goes through the stomach and digestive tract and whatever the body absorbs is what ends up in the blood, which is a relatively small amount and not enough to raise blood concentration
