Windmill Comparabiles Calcium Citrate Plus D3

Our assessment

The evidence shows that calcium and vitamin D are essential for bone health, but this specific product's data is limited. For this Windmill Comparabiles Calcium Citrate Plus D3 product, specific ingredient amounts, serving sizes, and clinical study data are not available. We can only assess the general ingredients: calcium citrate and vitamin D3. For calcium, the established RDA for most adults is 1,000 mg per day, increasing to 1,200 mg for women over 50 and men over 70 [NIH ODS]. For vitamin D, the RDA is 600 IU for adults up to age 70, and 800 IU for those over 70 [NIH ODS].

How it works

Think of calcium as the structural building block for your bones and teeth, and vitamin D as the key that unlocks calcium absorption in your gut [NIH ODS]. Calcium citrate is a form of calcium that can be taken with or without food, and it may be better absorbed by people with lower stomach acid [NIH ODS]. Vitamin D3 (cholecalciferol) is the form your body makes from sunlight and is more effective at raising blood levels than vitamin D2 [NIH ODS].

Safety profile

For this specific product, adverse event report data is not available. However, for calcium and vitamin D supplements generally, FDA data shows potential side effects. For calcium, reports include constipation (over 500 reports) and kidney stones (over 200 reports) [FDA data]. For vitamin D, reports include nausea (over 300 reports) and hypercalcemia (high blood calcium, over 100 reports) [FDA data]. You should not exceed the tolerable upper intake level of 4,000 IU per day for vitamin D without medical supervision [NIH ODS].

Our recommendation

Because specific dosage information for this product is not available, I cannot make a precise recommendation on this exact bottle. Your best step is to check the Supplement Facts panel on the label for the exact amounts of calcium and vitamin D per serving. Compare that to your dietary needs. For most adults, a supplement providing 500-600 mg of calcium and 600-800 IU of vitamin D is a reasonable starting point [NIH ODS]. If you are taking other medications, please consult your doctor, as calcium can interfere with thyroid medication and some antibiotics [NIH ODS].

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