Vitamin A

My primary care doctor let me know tonight that he wants me to start taking vitamin A......5000 mg per day!!!! Is that a huge amount or what?! Does anyone know what vitamin A is for? I just had my 6 month bloodwork done....well, last month. He must've gotten the results and then let me know tonight he wanted me to start taking 5000 mg of vitamin A. Any helpful answers would be greatly appreciated. Jen Halliday