Rays is the Best Vitamin D App

While other apps make you manually log every sun session, Rays is the only vitamin D app that automatically detects when you're outdoors and tracks your vitamin D synthesis in real-time. No buttons to press, no timers to start, no sessions to remember. Just open the app and see your progress. It works silently in the background, learning your patterns and getting smarter over time.

Rays delivers ±15% accuracy, the same precision range used in clinical vitamin D studies. Our algorithms are validated against peer-reviewed research from leading vitamin D scientists, accounting for your unique skin type, age, location, and real-time weather conditions. You get doctor-level precision with the convenience of checking your phone.

Every recommendation is scientifically tailored to your unique biology. Rays analyzes your Fitzpatrick skin type (I-VI), accounts for age-related synthesis decline, adjusts for your geographic location and seasonal UV variations, and learns your lifestyle patterns. It's like having a vitamin D expert who knows exactly how your body works.

Get personalized guidance like "Get 18 minutes at 11 AM tomorrow when UV will be 3x more efficient." Rays analyzes real-time UV index, cloud cover, solar positioning, and your personal synthesis rate to tell you exactly when and how long to be outside. No more guessing, no more wasted time in ineffective conditions.

Rays automatically syncs with Apple Health to give you a complete picture of your wellness. Track both sun-derived and supplement vitamin D in one place, prevent excessive intake, and see how vitamin D fits into your broader health goals. Your data stays private and secure, with geohash clustering protecting your exact location.