21st Century Calcium Citrate +D3 Maximum
Brand: 21st Century · Form: TABLET [E0155] On Market
Our assessment
The evidence shows that this product combines two well-studied nutrients for bone health. The data supports that calcium is essential for bone mineralization and neuromuscular relaxation [NIH ODS]. However, you should be aware that this is a high-dose formulation, and the risks associated with excessive calcium intake are significant. Our assessment: this supplement can be beneficial if you have a confirmed calcium deficiency, but it is not appropriate for everyone.
How it works
Think of calcium as a building block for your bones. It works through bone mineralization, supporting bone density and mineral deposition. It also plays a role in neuromuscular relaxation, helping your muscles relax and your nerves signal properly [NIH ODS]. The vitamin D3 in this formulation is added to enhance calcium absorption, though specific data on the D3 amount in this exact product is not provided.
Safety profile
FDA received 592,059 total adverse event reports across all supplement categories. For calcium specifically, high intakes might increase the risk of heart disease and prostate cancer. Side effects from high calcium levels include 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]. You should also note that calcium can reduce the absorption of medications such as bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS].
Our recommendation
Before taking this supplement, have your blood calcium levels checked by a healthcare provider. If you are currently taking any prescription medications, especially those listed in the interactions, take this supplement at a different time of day. Do not exceed the recommended dose on the label. For most adults, the goal is to meet, not exceed, the daily requirement from food and supplements combined. Start with a lower-dose calcium supplement if you are unsure of your needs [NIH ODS].
AI-assisted analysis. Data sourced from NIH DSLD.
Supplement Facts
| Brand | 21st Century |
|---|---|
| Serving Size | |
| Contents | 400.0 Tablet(s) |
| Market Status | On 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