Dr. Mercola Calcium With Vitamins D & K2

Our assessment

The evidence shows that this combination supplement addresses three key nutrients for bone health, but you need to be aware of specific risks. Calcium is essential for bone mineralization and neuromuscular relaxation [NIH ODS]. However, the data indicates that high calcium intakes might increase the risk of heart disease and prostate cancer [NIH ODS]. Our assessment is that this supplement could be appropriate if you have a confirmed need, but it is not for everyone.

How it works

Think of calcium as the building block for your bones, supporting bone density and mineral deposition [NIH ODS]. It also plays a critical role in neuromuscular relaxation, helping your muscles relax and your nerves signal properly [NIH ODS]. The addition of vitamins D and K2 is designed to help your body absorb and direct calcium to your bones rather than soft tissues, though specific data on this combination's efficacy is not provided in the available data.

Safety profile

The FDA has received 592,059 total adverse event reports for products containing these ingredients [FDA data]. Specific side effects from high calcium levels include poor muscle tone, poor kidney function, low phosphate levels, constipation, nausea, weight loss, extreme tiredness, frequent need to urinate, and abnormal heart rhythms [NIH ODS]. There is also a high risk of death from heart disease with excessively high levels [NIH ODS]. Data not available on the exact number of reports specific to this brand or the vitamin D and K2 components individually.

Our recommendation

Start by having your blood calcium and vitamin D levels tested before taking this supplement. If you take calcium, do not exceed the tolerable upper intake level without medical supervision. Be aware that calcium can reduce absorption of medications including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS]. Our recommendation is to prioritize getting calcium from food sources first and only use this supplement under the guidance of a healthcare professional who can monitor your levels and risks.

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