21st Century Calcium 500 + D3
Brand: 21st Century · Form: TABLET [E0155]
Our assessment
The evidence shows that 21st Century Calcium 500 + D3 provides a standard dose of calcium (500 mg) with vitamin D to support bone health. For most adults, the total daily calcium recommendation is 1,000 mg to 1,200 mg, so this supplement may help you meet your needs, especially if your diet is low in dairy or fortified foods [NIH ODS]. We recommend assessing your total calcium intake from food and other supplements before adding this product.
How it works
Think of this supplement as a structural support system for your bones. The calcium works through bone mineralization, helping maintain bone density and mineral deposition, while also supporting muscle relaxation and nerve signaling [NIH ODS]. This dual action helps keep your skeleton strong and your muscles functioning properly.
Safety profile
FDA received 592,059 total adverse event reports across all similar products, though this number includes all supplements and medications. Specific risks include that high calcium intakes might increase the risk of heart disease and prostate cancer [NIH ODS]. 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]. Calcium can also reduce the absorption of several medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS].
Our recommendation
Start by evaluating your daily calcium intake from food. If you need a supplement, take this product with food to improve absorption and spread doses throughout the day if taking more than one tablet. Be aware of the potential medication interactions, and space this supplement at least two hours apart from antibiotics or thyroid medication [NIH ODS]. Do not exceed the total daily recommended intake without a healthcare provider’s guidance, as the risks of high calcium intake are serious [NIH ODS].
AI-assisted analysis. Data sourced from NIH DSLD.
Supplement Facts
| Brand | 21st Century |
|---|---|
| Serving Size | |
| Contents | 90.0 Tablet(s) |
| Market Status | Off Market |
How to Read This Label
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