NOW Calcium & Magnesium

Our assessment

The evidence shows that calcium is essential for bone health, but your specific product’s data on effectiveness is limited. Calcium supports bone density and neuromuscular relaxation [NIH ODS]. However, we cannot confirm the exact dosage or bioavailability of the calcium in this specific NOW product without a complete label. Our assessment is that calcium is a well-studied mineral, but you should verify the elemental calcium content on the label to ensure it meets your needs.

How it works

Think of calcium as a structural building block for your skeleton. It works through bone mineralization, helping deposit minerals into your bone matrix to maintain density [NIH ODS]. It also plays a key role in neuromuscular relaxation, which means it helps your muscles relax and your nerves send signals properly after contraction [NIH ODS]. For this product, the magnesium may complement calcium by supporting muscle function, though specific data for the combination in this brand is not available.

Safety profile

Data not available for this specific product’s adverse events. However, for calcium generally, high intakes might increase the risk of heart disease and prostate cancer [NIH ODS]. High levels of calcium 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 [NIH ODS]. Calcium can also reduce the absorption of several medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS]. The FDA has received 592059 total adverse event reports across all supplements, but specific counts for this product are not available [FDA data].

Our recommendation

Start by reading the product label carefully to see the exact amount of elemental calcium and magnesium per serving. For most adults, 1,000-1,200 mg of calcium daily from all sources is a common target, but do not exceed that without medical supervision due to the risks of high intakes [NIH ODS]. Take calcium supplements separately from medications like thyroid hormone or antibiotics by at least 2 hours to avoid absorption issues [NIH ODS]. Our recommendation is to use this product as a general mineral support, but consult your doctor if you have a history of kidney stones, heart disease, or take prescription medications.

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