Comparison of Prescription 50,000 USP Vitamin D Vs. OTC

Vitamin D is commonly known for its role in bone health. Scientists now believe that the effects of vitamin D deficiency go beyond the skeletal system. A lack of vitamin D may also increase your risk for several chronic diseases, including cardiovascular disease, cancer, diabetes and autoimmune diseases. Many physicians are measuring vitamin D levels in their patients and recommending supplementation. Vitamin D supplements come in either a prescription form or an over-the-counter version.

Vitamin D supplements come in both prescription form and an over-the-counter version. (Image: Fuse/Fuse/Getty Images)

Prescription Vitamin D

The prescription version of vitamin D is called Drisdol, and it comes in 50,000 International Units of capsules. It is commonly prescribed to be taken once per week. Drisdol is ergocalciferol, which is the form of vitamin D that is derived from plants. Ergocalciferol is often referred to as vitamin D-2. This is different than cholecalciferol, or vitamin D-3, which is the form that is synthesized in the skin with exposure to ultraviolet B rays.

OTC Vitamin D

Both vitamins D-2 and D-3 are available in over-the-counter versions. They can easily be purchased in most drug stores and usually come in 400 International Units, 1,000 International Units, 2,000 International Units or 5,000 International Units of capsules. Because the doses are smaller than the prescription version, the OTC versions are intended to be taken daily. OTC vitamin-D is relatively inexpensive and a month's supply may even cost less than your insurance co-pay for the prescription version.

D-2 vs. D-3

One difference between prescription and OTC vitamin D is that the prescription version is only available as D-2, or ergocalciferol. Many scientists believe that ergocalciferol and cholecalciferol are comparable in potency, but ergocalciferol is broken down more quickly in the body. Therefore, cholecalciferol, or D-3, may be slightly more effective to raise the blood levels of vitamin D.

USP Verification

Another difference between prescription and OTC vitamin D is that the prescription version is USP verified. A supplement that is USP verified has been tested for quality and the ingredients have been examined. You can be sure that these supplements contain what the label claims they contain and free from contaminants. Dietary supplements are not regulated by a governmental agency, so the quality of OTC cannot be guaranteed. If you choose to purchase an OTC form of vitamin D, choose a brand with a reliable reputation.