Vitamin D wiped out my flu in about six hours. I took 45,000 IU spread out with food.

After six hours I only had a headache. I didn't know at the time it was probably caused by low magnesium levels. Your body used MG with D. Vitamin K2 is also a cofactor. Eat green leafy vegetable and nuts and seeds for MG, K2, and other cofactors of vitamin D. If I stopped taking 15k IU every time I ate, then the flu symptoms would start to come back.