NOW Calcium & Magnesium

Our assessment

Our assessment: The combination of calcium and magnesium in this supplement is a common pairing for bone and muscle health, but the evidence requires a careful look at dosing and safety. For calcium, the data confirms its role in bone mineralization and neuromuscular function [NIH ODS]. However, you need to be aware of the potential risks associated with high calcium intake, which are significant enough to warrant caution [NIH ODS].

How it works

Think of calcium as the structural building block for your bones and a key player in nerve signaling and muscle relaxation [NIH ODS]. Magnesium often works alongside calcium to support these processes. For calcium specifically, the mechanism is well-documented: it supports bone density and mineral deposition, and it helps regulate neuromuscular relaxation and nerve signaling [NIH ODS].

Safety profile

The FDA has received a total of 592,059 adverse event reports across all supplements, but specific report counts for this product are not available. For calcium, safety data shows that 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]. Additionally, calcium can reduce the absorption of several medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS].

Our recommendation

Our recommendation: Before starting this or any calcium supplement, consult your healthcare provider to determine if you need it, especially given the potential risks of high intake and medication interactions [NIH ODS]. If you do take it, be careful not to exceed the recommended dose on the label, and do not combine it with other high-dose calcium supplements without medical guidance. Data not available on the specific magnesium dose in this product, which is a key variable for safety and effectiveness.

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