It is estimated that over 40% of the US population has low vitamin D levels. Therefore, people 50 years old and above are at an increased risk of developing vitamin D deficiency. A simple blood test can determine your vitamin D level (a result of 20 ng/mL to 50ng/mL is considered adequate for healthy people) and can help you select the right supplement dosage along with a discussion with your doctor. Health Thru Nutrition offers pure vitamin D-3, as cholecalciferol, in three Health Thru Nutrition manufactures its Vitamin D-3 under strict cGMP standards in the USA. All strengths are non-GMO, contain no artificial sweeteners or preservatives, are free of soy and gluten, and contain no major allergens.