I would like to lighten my skin using the glutathione pills, I'm light skinned with yellow undertone.How much mg should I take to be 3-4 shades lighter. Also how many mg of vit c should I take?

Honey. Those pills do not work. You're wasting your money. No amount will make you lighter, unless it has some type of placebo effect.

I agree these pills are a big waste of money. I haven't heard of anyone who has lightened with them ever!

You can try Obagi vitamin c serum,
http://www.amazon.com/Obagi-Professional-C-Serum-20-1oz/dp/B000VMRLBS
Or beauty mia Veclo vitamin c lotion
http://vitaminc.dayscience.com
Or Vitamin C serum by Dr. Jo
http://www.natural-skin-care-info.com/vitamin-c-serum.html