It is estimated that over 40% of our population has low vitamin d levels. Unfortunately, as we age, our ability to convert dietary vitamin d into its active form diminishes, as does our ability to synthesize vitamin d from sunshine, reducing our body’s vitamin d levels further. 
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 different strengths, 2000iu, 5000iu, and 10,000iu, the most potent available.  
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.