Always exhausted? It may not be stress or stretching yourself too thin. Find out the real medical reason you're exhausted. Dr. Oz set up his own lab and uncovered the 4 secret reasons you're over-tired.

Click here for Part 1 of Dr. Oz's Exhaustion Lab.

Click here for Part 2 of Dr. Oz's Exhaustion Lab.

Want to know how to look marvelous without splurging so much? Dr. Oz invites three beauty experts to share the smartest ways to save money while looking fabulous starting from your hair and makeup tools to the beauty products you use.