NOW Calcium Citrate 100% Pure Powder

Our assessment

The evidence shows that calcium is essential for bone health, but the form and dosing matter significantly. For NOW Calcium Citrate 100% Pure Powder, our assessment is that it is a well-absorbed form of calcium, making it a suitable option for many people, especially those with lower stomach acid or those taking acid-reducing medications. However, you must be careful with dosing, as the data highlights important safety considerations at high intakes [NIH ODS].

How it works

Think of calcium as a builder and messenger for your body. It supports bone mineralization, helping to maintain bone density and structure. At the same time, it plays a key role in neuromuscular relaxation, helping your muscles relax and your nerves signal properly after contraction [NIH ODS].

Safety profile

The data shows a large number of adverse event reports for calcium-containing supplements, with a total of 592,059 reports across the FDA database [FDA data]. High intakes of calcium can lead to serious risks. These include constipation, nausea, weight loss, extreme tiredness, frequent urination, and abnormal heart rhythms. High levels in the blood and urine can also cause poor muscle tone, poor kidney function, low phosphate levels, and a high risk of death from heart disease [NIH ODS]. You should also be aware that calcium can reduce the absorption of several medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS].

Our recommendation

Start by assessing your total daily calcium intake from food and other supplements. Do not exceed the tolerable upper intake level without medical supervision. Because this is a pure powder, you can adjust your dose precisely, but take it with food to improve absorption. Separate your calcium dose from any medications listed in the interactions section by at least two hours. We recommend consulting your healthcare provider to check your blood calcium levels and kidney function before starting a high-dose regimen [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