Os-Cal Calcium+D3

Our assessment

The evidence shows that Os-Cal Calcium+D3 is a well-established supplement for supporting bone health. Our assessment is that this product can be a reliable way to meet your calcium and vitamin D needs, but you must be aware of important safety considerations and potential medication interactions.

How it works

The calcium in this supplement plays a central role in bone mineralization, helping to maintain bone density and support the deposition of minerals into your skeleton [NIH ODS]. It also acts as a neuromuscular regulator, supporting muscle relaxation and proper nerve signaling throughout your body [NIH ODS]. The added vitamin D3 helps your body absorb the calcium more effectively.

Safety profile

FDA has received a total of 592,059 adverse event reports across all supplement categories, though specific event counts for this product are not available in the data. Regarding calcium, high intakes may increase the risk of heart disease and prostate cancer [NIH ODS]. High levels of calcium in your blood and urine can cause poor muscle tone, poor kidney function, low phosphate levels, constipation, nausea, weight loss, extreme tiredness, frequent urination, abnormal heart rhythms, and a high risk of death from heart disease [NIH ODS]. Calcium can also reduce the absorption of several medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS].

Our recommendation

We recommend taking Os-Cal Calcium+D3 with food to improve absorption. Take it at least two hours apart from any medications listed in the interactions, such as thyroid medication or antibiotics [NIH ODS]. Do not exceed the recommended dose on the label, and consult your doctor before starting if you have a history of kidney stones, heart disease, or prostate cancer. For most adults, total calcium intake from food and supplements should be carefully monitored to avoid excessive levels [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