21st Century Calcium 500 + D3
Brand: 21st Century · Form: TABLET [E0155]
Our assessment
The evidence shows that this product provides a standard dose of calcium and vitamin D3 for bone support. For most adults, calcium intake from food and supplements should total 1,000 mg daily, with vitamin D at 600 IU [NIH ODS]. This supplement delivers a specific amount of calcium, but you must check your total daily intake from all sources to avoid exceeding safe upper limits.
How it works
Think of calcium as a structural building block for your bones and a signal conductor for your nerves and muscles. It supports bone mineralization and density, and helps with muscle relaxation and nerve signaling [NIH ODS]. Vitamin D3 helps your body absorb the calcium you take in, making the two nutrients a team for skeletal health.
Safety profile
FDA received 592,059 total adverse event reports across all supplements, but specific report counts for this product are not available. Some research suggests 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 total daily calcium intake from food. If you already consume dairy, fortified foods, or leafy greens, you may not need this supplement. Take it with food for best absorption. Separate this supplement from thyroid medication or antibiotics by at least 4 hours [NIH ODS]. Do not exceed 2,000 mg of total calcium per day from all sources without consulting your doctor [NIH ODS].
AI-assisted analysis. Data sourced from NIH DSLD.
Supplement Facts
| Brand | 21st Century |
|---|---|
| Serving Size | |
| Contents | 400.0 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