21st Century Calcium Citrate + D3 Maximum
Brand: 21st Century · Form: TABLET [E0155]
Our assessment
The evidence shows that this product provides two well-studied nutrients, but you need to be careful with dosing. Calcium is essential for bone health, and vitamin D3 helps your body absorb it. However, you should not exceed the recommended daily allowance without medical supervision. Data on the exact calcium and vitamin D3 amounts in this specific product is not available, so you must check the Supplement Facts panel on the bottle.
How it works
Think of calcium as the building material for your bones and teeth. It supports bone density and mineral deposition, and it also plays a key role in muscle relaxation and nerve signaling [NIH ODS]. Vitamin D3 acts as a helper — it improves how well your body absorbs calcium from your digestive tract. Together, they work to maintain strong bones and proper muscle function [NIH ODS].
Safety profile
Total FDA adverse event reports for this product line are 592059 [FDA data]. The main risks come from calcium. High calcium intakes might increase the risk of heart disease and prostate cancer. Very high levels in the blood can cause poor muscle tone, poor kidney function, constipation, nausea, weight loss, extreme tiredness, frequent urination, abnormal heart rhythms, and a high risk of death from heart disease [NIH ODS]. Calcium can also reduce the absorption of certain medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS].
Our recommendation
Start by checking the label for the exact amount of calcium and vitamin D3 per serving. Do not take more than the recommended dose unless your doctor advises it. Take this supplement with food for best absorption. If you take any of the medications listed above, separate your supplement by at least 2 hours [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