21st Century Calcium Citrate +D3 Regular
Brand: 21st Century · Form: TABLET [E0155] On Market
Our assessment
The evidence shows that this combination supplement provides two key nutrients for bone health. Calcium citrate is a well-absorbed form of calcium, and vitamin D3 helps your body use that calcium effectively. For most adults, this is a reliable option to support your daily intake, but it is essential to check your total calcium from all sources — food plus supplements — to avoid exceeding safe levels [NIH ODS].
How it works
Think of calcium as the building material for your bones and teeth, supporting bone density and mineral deposition. Vitamin D3 acts as the delivery system, helping your body absorb that calcium from your digestive tract. Together, they also support neuromuscular relaxation and nerve signaling [NIH ODS].
Safety profile
FDA received 592,059 total adverse event reports for this product category. The main safety concern is getting too much calcium. High intakes may increase the risk of heart disease and prostate cancer. Signs of excessive calcium include constipation, nausea, weight loss, extreme tiredness, frequent urination, abnormal heart rhythms, and poor kidney function [NIH ODS] [FDA data]. Also, calcium can reduce the absorption of certain medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS]. Data on specific side effect counts for this exact product is not available.
Our recommendation
Start by checking your daily calcium intake from food. If you need a supplement, this product is a good choice, especially if you take it with a meal for best absorption. Take it at least two hours apart from any medications listed above. Do not exceed the tolerable upper intake level for calcium without your doctor’s guidance [NIH ODS].
AI-assisted analysis. Data sourced from NIH DSLD.
Supplement Facts
| Brand | 21st Century |
|---|---|
| Serving Size | |
| Contents | 120.0 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