Amidst the endless sea of vitamin/mineral supplements available today, determining which forms of the nutrients are the best, which products are worth the money, and ultimately what products are safe is anything but easy.

The U.S. Government’s attempt to help consumers was to assign a Daily Value (DV) to various vitamins, minerals, fats, protein, carbohydrates, and fiber. A DV percentage now appears on all dietary supplement labels within the product’s Supplement Facts box. If a supplement contains the exact DV, then it is listed as 100% DV; if it contains twice the DV, then it is listed as 200% DV.

The percent DV is the source of a lot of confusion

Over the years, numerous U.S. Government recommendations – a veritable alphabet soup (RDA, RDI, DRI, AI, UL, etc.) – have suggested the amounts of specific nutrients needed to stay healthy. To complicate matters, there were often different recommended amounts for men and women. For example, the recommended amount for vitamin C for women was 75 mg, but for men it was 90 mg.

So the Daily Values were established to provide one number that would be designated on food labels and on dietary supplement labels. There are four categories of DVs: (1) infants to age 12 months, (2) children ages 1-3, (3) adults and children 4 and over, and (4) pregnant and lactating women.

What shows up on a label is “%DV” – which refers to the percentage of the DV in one serving. For most Thorne supplements, the %DV is for “adults and children age 4 and over” unless noted otherwise.

DVs are determined based on the amount of a specific nutrient that is expected to be sufficient for 97% of healthy individuals. You might be familiar with the term RDA (Recommended Dietary Allowance) and be wondering what happened to it. The RDA was created in 1941 by the Food and Nutrition Board. Over the years, the way RDAs were determined changed and expanded, eventually morphing into the currently used DVs.

Why can the %DV on a supplement label sometimes be so high?

Thorne is often asked why the %DV for a particular vitamin or mineral is sometimes so high. Keep in mind that the DVs are what the U.S. Government has determined is the amount just above what is needed to keep from developing a specific nutrient-deficiency disease, such as scurvy from being deficient in vitamin C.

Vitamin C was discovered when 18th century British sailors, who had been at sea for months, ran out of fresh fruits and vegetables so their diets consisted of no sources of vitamin C. Eventually, when the missing nutrient was discovered, British sailors would take lime juice on voyages – which prevented scurvy and resulted in the Brit nickname “Limey.”

Although the recommended amount of vitamin C has increased over the years – the DV is now 90 mg – that may be not the amount needed to support optimal health, and the optimal amount can far exceed the DV. For example, one capsule of Thorne’s Ascorbic Acid contains 1,000 mg of vitamin C – or 1,111% of the DV. But one serving of many fruits contains well above the DV too; for example, one cup of guava provides 377 mg of vitamin C – more than 400 percent of the DV.

Why is it important to get plenty of vitamin C?

Vitamin C is required for the biosynthesis of collagen and neurotransmitters and for the absorption of iron.* It serves as an important antioxidant in the body by limiting the damaging effects of free radicals through its antioxidant activity, and regenerating other antioxidants like vitamin E.* One of vitamin C’s most important roles is for immune function.*

Research suggests that the amount typically provided in a good quality dietary supplement (1,000 mg) is needed to support optimal immune function.*1 

Furthermore, because the potential for harm from taking too high an amount of vitamin C is so low, no “tolerable upper intake level” – the highest daily intake amount likely to pose no risk of adverse health effects – has been established for vitamin C. Vitamin C is a water-soluble vitamin, so what your body doesn’t use it excretes. A loose stool is about the worst thing that can happen from taking too much vitamin C.

When monitoring blood levels of certain nutrients, an amount significantly higher than the DV is often required to raise the nutrient’s blood level to within the normal range. Vitamin D is a good example of this.

The Endocrine Society’s guidelines suggest that an amount, under medical supervision, as high as 10,000 IU of vitamin D daily might be necessary to achieve sufficient levels, particularly in an individual with a higher body weight.2 The absence of toxicity in trials conducted in healthy adults who used 10,000 IU vitamin D3 daily supports the safety of this recommendation.3,4

If you take a higher amount of vitamin D, then it’s important to monitor its blood level and work with your health-care professional to determine optimal daily supplementation.

Other examples that often far exceed the DV are Thorne products that contain the water-soluble B vitamins. For example, vitamin B12’s DV (as methylcobalamin) of 2.4 mcg is far below the amount used in studies to support optimal nerve function – several of which used 1,500-3,000 mcg daily.*5 That would mean the amount of methylcobalamin used in studies to help individuals with nerve discomfort was between 625 and 1,250 times the amount of its DV. 

Thorne’s Methylcobalamin contains 1,000 mcg of vitamin B12 per capsule (417 times the DV). This is what Mayo Clinic says about the safety of vitamin B12:

“When taken at appropriate doses, vitamin B12 supplements are generally considered safe. While the recommended daily amount of vitamin B12 for adults is 2.4 micrograms, you can safely take higher doses. Your body absorbs only as much as it needs, and any excess passes through your urine.”6

Why take more vitamin B12 than the DV? Fifteen percent of the general population is thought to be deficient in vitamin B12, which is needed to make red blood cells, nerve tissue, and DNA, plus vitamin B12 is required for healthy cardiovascular function and proper nerve function.*

Vegans, the elderly, elite athletes, and individuals who have certain genetic polymorphisms have a higher need for vitamin B12.*  During pregnancy and lactation, a higher amount is needed to support the needs of the mother and the added needs of the developing baby.* Vitamin B12, along with folate, is considered one of the most important nutrients during pregnancy because it’s essential for the development of the nervous system.*

Rather than supplying formulas with nutrient content to simply prevent a deficiency, Thorne incorporates the amounts of nutrients that support optimal health for a wide range of individuals, including those with less than ideal diets. So although the high %DVs on the labels of some Thorne products, like Basic Prenatal, can be confusing, our team of medical experts ensure that the amounts of nutrients in all our formulas are both effective AND safe.   


  1. Carr A, Maggini S. Vitamin C and immune function. Nutrients 2017;9(11).
  2. [Accessed Sept. 11, 2019]
  3. Hathcock J, Shao A, Vieth R, Heaney R. Risk assessment for vitamin D. Am J Clin Nutr 2007;85(1):6-18.
  4. [Accessed Sept. 11, 2019]
  5. Head K. Peripheral neuropathy: pathogenic mechanisms and alternative therapies. Altern Med Rev 2006;11(4):294-329.
  6. [Accessed Sept. 11, 2019.]