What's Rhonda Patrick's guidance on Vitamin D supplementation?

Rhonda Patrick’s guidance is to use vitamin D3 supplementation when needed, but tailor the dose to measured blood levels. She says she personally takes 5,000 IU daily and her level stays around 50 ng/mL. 1

• 5,000 IU and expected response: Patrick says 5,000 IU daily keeps her vitamin D level around 50 ng/mL. For many people without relevant genetic variants, she estimates that 1,000 IU raises blood levels by about 5 ng/mL. 2 1
• Testing: Measure vitamin D levels before and after supplementing to see how your body responds; she especially emphasizes this because common genetic variants can impair vitamin D metabolism. 3
• Safety and upper limit: She describes hypercalcemia as very difficult to develop, citing extremely high daily amounts taken over a long time; she also notes that the Institute of Medicine set the upper tolerable intake at 4,000 IU. 4
• Sun and food sources: Sun exposure helps the skin make vitamin D3, while fortified foods such as milk and fatty fish can provide vitamin D; she cautions that eating fish alone is unlikely to correct a deficiency. 5