Swanson Premium Brand Vitamin D 400 IU (10 mcg)

Our assessment

The evidence shows that this product provides 400 IU of vitamin D, which is a standard maintenance dose for many adults. However, data for the specific ingredient in this supplement — calcium — is provided, not vitamin D. Our assessment is that while 400 IU is a safe starting point, you need to be aware that the safety data available pertains to calcium, not vitamin D [NIH ODS].

How it works

Think of calcium as a structural and signaling mineral. It supports bone mineralization and density, and it plays a key role in neuromuscular relaxation and nerve signaling [NIH ODS]. If you are taking this vitamin D supplement to help with calcium absorption, the mechanism is indirect: vitamin D helps your body absorb calcium from food.

Safety profile

FDA has received a total of 592,059 adverse event reports across all supplements. For calcium specifically, high intakes might increase the risk of heart disease and prostate cancer. High levels of calcium in the blood and urine can cause poor muscle tone, poor kidney function, low phosphate levels, constipation, nausea, weight loss, extreme tiredness, frequent need to urinate, abnormal heart rhythms, and a high risk of death from heart disease [NIH ODS]. Side effect report counts for vitamin D specifically are not available in the provided data.

Our recommendation

Start with 400 IU daily, which is a common baseline amount. However, data on the specific side effects and interactions for vitamin D in this product are not available. Note that calcium supplements can reduce the absorption of medications like bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS]. For personalized advice, consult your healthcare provider.

Supplement labels contain several key sections regulated by the FDA:

• Serving Size — The recommended amount per dose. Always check this — some products require multiple capsules per serving.
• Amount Per Serving — Shows the quantity of each nutrient in the product, typically in IU (International Units), mg (milligrams), or mcg (micrograms).
• % Daily Value (%DV) — Indicates how much a nutrient in a serving contributes to a daily diet. 5% DV or less is low; 20% DV or more is high.
• Other Ingredients — Lists inactive ingredients like fillers, binders, and capsule materials (e.g., gelatin, cellulose, magnesium stearate).
• Suggested Use — The manufacturer's recommended directions for taking the supplement, including timing and dosage.

Source: FDA Dietary Supplement Labeling Guide