21st Century Calcium Citrate +D3 Maximum
Brand: 21st Century · Form: TABLET [E0155] On Market
Our assessment
Our assessment: The combination of calcium and vitamin D3 in this supplement is well-supported for bone health, but you need to be precise about dosage and timing. The data shows that calcium supports bone mineralization and neuromuscular relaxation [NIH ODS]. However, you must be aware that high calcium intakes might increase the risk of heart disease and prostate cancer [NIH ODS].
How it works
Think of calcium as the structural building block for your bones and teeth, while vitamin D3 acts as the delivery system that helps your body absorb that calcium. Calcium supports bone density and mineral deposition, and it also helps your muscles relax and your nerves signal properly [NIH ODS]. Without enough vitamin D, your body cannot use the calcium you consume effectively.
Safety profile
FDA received a total of 592,059 adverse event reports across this product category. The specific safety concerns for calcium include: high levels 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 [FDA data] [NIH ODS]. You should also know that calcium can reduce the absorption of several medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS]. Data not available for specific side effect counts per individual symptom.
Our recommendation
Take this supplement with food to improve absorption, and separate it from any thyroid medication or antibiotics by at least two hours [NIH ODS]. Do not exceed the recommended dose on the label, as high calcium intakes carry serious risks. If you have a history of kidney stones, heart disease, or prostate cancer, consult your doctor before starting this supplement [NIH ODS].
AI-assisted analysis. Data sourced from NIH DSLD.
Supplement Facts
| Brand | 21st Century |
|---|---|
| Serving Size | |
| Contents | 75.0 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