NOW Magnesium Citrate 200 mg

Our assessment

The evidence shows that calcium is a critical mineral for bone health, but it is not the primary ingredient in the product you asked about. Since the product is NOW Magnesium Citrate 200 mg, our assessment must focus on calcium as a separate mineral. The data confirms that calcium supports bone mineralization and neuromuscular relaxation [NIH ODS]. However, you should be aware that calcium supplements can interact with several medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS].

How it works

Think of calcium as a structural builder and signaler — it supports bone density and mineral deposition, and it helps your muscles relax and your nerves signal properly [NIH ODS]. The data does not provide specific information on how calcium works in combination with magnesium citrate, so you should consider taking them at separate times if you are using both.

Safety profile

The FDA received 592,059 total adverse event reports across all supplements, but the specific number for calcium alone is not provided [FDA data]. The data warns that high calcium intakes might increase the risk of heart disease and prostate cancer. 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]. Data not available for side effects specific to this product.

Our recommendation

Since you are taking NOW Magnesium Citrate 200 mg, do not add a calcium supplement without consulting your healthcare provider. If you need calcium, check your total intake from food and any other supplements. The data shows calcium can reduce absorption of key medications, so take it at least two hours apart from any drugs you use [NIH ODS]. Start with food sources first, as the safety data highlights real risks with high-dose supplements [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