21st Century Calcium Citrate +D3 Maximum
Brand: 21st Century · Form: TABLET [E0155]
Our assessment
The evidence shows that this product combines two well-studied nutrients. Calcium supports bone mineralization and neuromuscular relaxation, while vitamin D3 aids calcium absorption [NIH ODS]. For most adults, the combination is a reasonable choice to support bone density, provided you do not exceed the recommended daily allowance from all sources.
How it works
Think of calcium as the primary building block for your skeleton. It works through two main mechanisms: bone mineralization to support bone density and mineral deposition, and neuromuscular relaxation to support muscle relaxation and nerve signaling [NIH ODS]. The vitamin D3 in this product helps your body absorb and use the calcium effectively.
Safety profile
FDA received 592,059 total adverse event reports for products in this category. Specific side effects from calcium supplements can include constipation, nausea, and weight loss [FDA data]. High calcium intakes might increase the risk of heart disease and prostate cancer [NIH ODS]. Very high levels of calcium in the blood can cause poor muscle tone, poor kidney function, low phosphate levels, extreme tiredness, frequent need to urinate, abnormal heart rhythms, and a high risk of death from heart disease [NIH ODS]. Calcium can reduce the absorption of bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS].
Our recommendation
Start by checking your total calcium intake from food and other supplements to avoid exceeding the RDA. Take this supplement with food for best absorption. If you take any medications — especially for thyroid, osteoporosis, or infections — separate your calcium dose by at least two hours [NIH ODS]. Data not available on the exact dosage per tablet in this specific product, so follow the label instructions.
AI-assisted analysis. Data sourced from NIH DSLD.
Supplement Facts
| Brand | 21st Century |
|---|---|
| Serving Size | |
| Contents | 75.0 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