Tip You've probably heard that eight hours is the magic number when it comes to your nightly sleep needs, but that's not entirely accurate. Most adults need between seven and eight hours of sleep each night, but some people may need a bit less and others a bit more (like nine or even 10), says , a board-certified physician, certified sleep specialist and founder of . If you're in the latter group, you'll likely still feel tired after sleeping only seven or eight hours., You've probably heard that eight hours is the magic number when it comes to your nightly sleep needs, but that's not entirely accurate. Most adults need between seven and eight hours of sleep each night, but some people may need a bit less and others a bit more (like nine or even 10), says Angela Holliday-Bell, MD, a board-certified physician, certified sleep specialist and founder of , Anemia and Fatigue. Symptoms: Fatigue, dizziness, feeling cold, crankiness. Anemia is the most common blood condition in the U.S. It affects more than 5.6% of Americans. For women in their .