NOW Magnesium & Calcium

Our assessment

The evidence shows that this supplement combines two essential minerals, but you need to be aware of the specific benefits and risks for each. Calcium is well-supported for bone health, while magnesium supports muscle and nerve function. However, data for this specific combination product is limited, so we rely on the ingredient-level data available [NIH ODS].

How it works

Calcium acts as a structural building block for your bones, supporting bone density and mineral deposition. It also plays a role in neuromuscular relaxation by supporting muscle relaxation and nerve signaling [NIH ODS]. The magnesium component complements this by further aiding muscle and nerve function. Think of this combination as supporting your body’s structural framework and communication system.

Safety profile

Data not available for this specific product’s adverse event reports. However, for calcium, some research suggests that high intakes might increase the risk of heart disease and prostate cancer. High levels 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 total FDA adverse event reports for all supplement products is 592,059, but specific data for this product is not available [FDA data].

Our recommendation

Start by evaluating your dietary intake of calcium and magnesium. If you take this supplement, take it with food to improve absorption. Because calcium can interfere with certain medications, take it at least 2 hours apart from any prescriptions. Monitor for side effects like constipation or nausea. If you have a history of kidney disease, heart disease, or prostate cancer, consult your doctor before use [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