Kirkland Signature Calcium Citrate, Magnesium, and Zinc

500 Tablets
Signature calcium citrate, magnesium, and zinc supplement with vitamin D3 for strong bones, teeth, and muscles.
Best For
Those with bone issues /malabsorption & metabolism issues with calcium [11-12]; Enhanced immune system, heart, teeth, bone, and muscle health [1-10]
What's in It 500mg of calcium, > 80mg of magnesium, 20mg Vitamin D3, 10mg Zinc (Verified By USP)
Ingredients of Concern

Croscarmellose sodium (linked to allergies)

Purity Tested: Passed tests for contaminants (See USP Verification)

  • Gluten-free
  • Yeast-free
    • Pros:
    • High potency calcium citrate supplement with magnesium, zinc, and vitamin D3 for enhanced overall health
    • Ensures proper transportation of calcium into the teeth, bones, and muscles
    • Helps support the body's ability to fight different health problems
    • Lowers the risk of physical fatigue and muscle cramps
    • Lowers the risk of developing bone-related issues
    • Supports healthy muscle contraction and relaxation
    • USP Verified
    • No artificial colors or flavors
    • United States Pharmacopeia (USP) Verified Product
    The USP Verified Mark on the label indicates that this product:
    1. Contains the ingredients listed on the label, in the declared potency and amount
    2. Does not contain harmful levels of specified contaminants
    3. Will break down and release into the body within specified amount of time
    4. Has been made using safe, sanitary and well-controlled manufacturing practices according to FDA and USP guildelines

    Ingredients Concern: Croscarmellose sodium

    Cons: Zinc may interact with certain medications

    Costco created the Kirkland Signature brand as part of its private label products. They do not grow or produce anything but rather partner with other companies to produce the products. They are often sold a great value compared to the brand name products that they have in their store. Some of their products are quite good and in fact, Kirkland Signature's calcium was voted the best for customer satisfaction in the Consumer Trends and Preferences Report (2020) from ConsumerLabs. However, we dont like the addition of titanium dioxide to their supplements which is toxic.

    Magnesium heightens the activity of vitamin D3 and in doing so, enhances calcium transportation throughout the body, especially the bones, teeth, and muscles [1-4]. Vitamin D3 is more effective at raising and maintaining optimal levels of vitamin D in the blood than vitamin D2; thusly it is recommended by numerous clinical studies for bone and muscle health [5, 6]. In addition, vitamin D3 is more potent, more stable, and has a longer half-life than vitamin D2 [5, 6]. Zinc is an essential mineral for the proper growth and maintenance of almost all of the processes in the human body. It is especially vital for immune function, wound healing, blood clotting, thyroid function, and bone growth [8-10]

    Based on peer reviewed studies and science, it is recommended to maintain calcium intake from 500-1000 mg day for older individuals at risk of osteoporosis, but there seems to be little need for calcium supplements except in individuals with major malabsorption problems or substantial abnormalities of calcium metabolism. Therefore, it is important to consult with a doctor before taking calcium. [11].

    Research indicates that widespread use of calcium supplements in individuals without a specific bone issue is not helpful, and may cause harm. Also, vitamin D supplements should be reserved for those with vitamin D deficiency or risk factors, principally low sunlight exposure or dark skin and not living in a sunny environment. These recommendations are consistent with those of the United States Preventive Services Task Force, which also does not support the use of either calcium or vitamin D supplements in otherwise healthy adults that live in communities. The position of the International Osteoporosis Foundation is similar in that supplementation with calcium alone for fracture reduction is not supported by the literature but that calcium supplementation, with concomitant vitamin D supplementation, is supported for patients at high risk of calcium and vitamin D insufficiency [12].


    Those with bone issues /malabsorption & metabolism issues with calcium [11-12]; Enhanced immune system, heart, teeth, bone, and muscle health [1-10]
    Magnesium promotes the transfer of calcium into bones by accelerating the activity of vitamin D3 [1]. It also plays a role in the formation of hard tooth enamel that resists acid-induced tooth decay [2]. Without magnesium, calcium cannot be properly transported to the bones and teeth, and would instead begin to accumulate in organs such as the kidneys or liver [1, 2]. In addition, magnesium promotes muscle contraction and relaxation [3]. Low levels of magnesium are associated with electrolyte disorders and may contribute to the development of muscle fatigue, cramps, and spasms [3]. Furthermore, magnesium supports heart health by influencing electrical signals that regulate the heartbeat [4]. In addition, magnesium helps lowers the accumulation of fatty/lipid (plaque) build up in the arteries and it improves blood flow, which supports optimal blood pressure [4]. Vitamin D3 raises the concentration of calcium and phosphorus as theses nutrients work together to facilitate the growth of new bone [5-7]. More specifically, vitamin D3 ensures the body properly transports calcium into the bones where it is used to build layers of strong bone tissue; the absence of adequate calcium levels in the bones causes them to become brittle and prone to fracture [7]. There are over 300 different enzymes the need zinc in order to properly function [8-10]. In addition, a zinc deficiency may lead to growth problems, blood pressure issues, poor bone growth, and many other health problems [8].

    Key Ingredients: Calcium - 500 mg, Magnesium - 80 mg, Zinc - 10 mg, Vitamin D3 - 800 IU

    All Ingredients: Calcium citrate, Mangesium Oxide, Cellulose (Plant Origin), Croscarmellose Sodium, Magnesium Stearate, Silicon Dioxide, Pyridoxine Hydrochloride, Cellulose Coating, Zinc Oxide, Sodium Borate, Manganese Gluconate, Copper Gluconate, Boric acid, Glycine, Cholecalciferol

    (We are happy that Titanium Dioxide coloring was removed from this product.)

    Take two (2) tablets daily, preferable with a meal.
    These statements have not been evaluated by the FDA. These products are not intended to diagnose, treat, cure or prevent any disease.
    1. Castiglioni S, Cazzaniga A, Albisetti W, Maier JA. Magnesium and osteoporosis: current state of knowledge and future research directions. Nutrients. 2013;5(8):3022-33.
    2. Klimuszko E, Orywal K, et al. Evaluation of calcium and magnesium contents in tooth enamel without any pathological changes: in vitro preliminary study. Odontology. 2018;106(4):369-376.
    3. Dominguez LJ, Barbagallo M, et al. Magnesium and muscle performance in older persons: the InCHIANTI study. Am J Clin Nutr. 2006;84(2):419-26.

    4. Douban S, Brodsky MA, Whang DD, Whang R. Significance of magnesium in congestive heart failure. Am Heart J 1996;132:664-71.
    5. Armas LA, Hollis BW, Heaney RP. Vitamin D2 is much less effective than vitamin D3 in humans. J Clin Endocrinol Metab 2004;89:5387-91.
    6. Wolpowitz D, Gilchrest BA. The vitamin D questions: how much do you need and how should you get it? J Am Acad Dermatol. 2006;54(2):301-17
    7. Cranney A, Horsley T, O'Donnell S, et al. Effectiveness and safety of vitamin D in relation to bone health. Evid Rep Technol Assess (Full Rep). 2007;(158):1-235.
    8. Barceloux DG. Zinc. J Toxicol Clin Toxicol 1999;37:279-92.
    9. Walker, C. L. and Black, R. E. Zinc for the treatment of diarrhoea: effect on diarrhoea morbidity, mortality and incidence of future episodes. Int J Epidemiol. 2010;39 Suppl 1:i63-i69.
    10. Capdor J, Foster M, Petocz P, Samman S. Zinc and glycemic control: a meta-analysis of randomised placebo controlled supplementation trials in humans. J Trace Elem Med Biol. 2013;27(2):137-42.
    11. Reid, I. R., S. M. Bristow, and M. J. Bolland. "Calcium supplements: benefits and risks." Journal of internal medicine 278.4 (2015): 354-368.
    12. Reid, Ian R., and Mark J. Bolland. "Calcium and/or vitamin D supplementation for the prevention of fragility fractures: who needs it?." Nutrients 12.4 (2020): 1011.
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