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Circadian Rhythms

Circadian rhythms are the 24-hour cycles of physical and mental changes that are driven by your body's "biological clock." They are influenced both by things inside your body and by things in your environment, especially light. Your circadian rhythms affect your sleep-wake cycle, your body temperature, and other important body functions.

Decision Points

Our interactive Decision Points guide you through making key health decisions by combining medical information with your personal information.

You'll find Decision Points to help you answer questions about:

Interactive Tools

Get started learning more about your health!

Our Interactive Tools can help you make smart decisions for a healthier life. You'll find personal calculators and tools for health and fitness, lifestyle checkups, and pregnancy.

Symptom Checker

Feeling under the weather?

Use our interactive symptom checker to evaluate your symptoms and determine appropriate action or treatment.