The Sunshine Vitamin in Just One Drop Mom's Choice Awards Honoring Excellence 600 IU Per Drop A Factor in the Maintenance of Good Health Dietary Supplement 100 Drops Euro Dropper Technology NSF Contents Tested & CertifiedVitamin D is made in the skin when exposed to summer sunshine (UVB) and is present in only a few foods.Vitamin D is necessary for healthy bones and normal muscle function.Vitamin D can be measured with a blood test for 25-Hydroxyvitamin D. The Institute of Medicine recommends this level should be higher than 20 ng/mL.A vitamin D supplement may be required to raise 25-Hydroxyvitamin D to healthy levels. Research findings show a 25 (OH) D blood level above 20 ng/mL is related to better health. A vitamin D3 supplement may be especially helpful for anyone who avoids exposing skin to sunshine.