Founded in the United States in 1935, GNC has been ranked No. 1 in the United States as the No. 1 franchise brand for vitamins and nutritional foods for four consecutive years. As an industry standard reference, its quality control system was selected by the U.S. FDA as a template for dietary supplement products. As brand marketing mainly relies on traditional brick-and-mortar retail, GNC, as a health care product giant, has seen sales stagnate in recent years under the impact of e-commerce brands. Not only that, in 2015, GNC was sued for adding banned ingredients Picameron and amphetamines, and the company's credibility was often questioned.
 
GNC's dietary supplements are often not cost-effective, with the exception of calcium supplements, which have been widely acclaimed. There are many types of branded calcium supplements, but in fact, most of them are not significantly different, except for slight changes in the amount of calcium and mineral additions. These calcium supplements are mainly divided into four types: calcium, calcium and magnesium, calcium and vitamin D, and calcium and magnesium vitamin D. Because vitamin D is not readily available in food, calcium containing vitamin D is recommended, especially in people who are deficient in the sun. In addition, if there is no serious calcium deficiency, it is recommended to buy calcium tablets with a lower calcium amount, and calcium citrate can be selected for those with weak digestive function.
 
The recommended dosage of GNC Calcium Citrate 1000mg is 1000mg of calcium/day, which is in line with the recommended intake of calcium in the United States, and higher than the recommended intake in China. However, compared with most high-calcium calcium tablets, this calcium tablet has a more detailed design, each tablet contains only 250mg of calcium, and consumers can flexibly choose to take 1-4 calcium tablets per day according to their own health conditions and dietary habits. The caplets of this calcium supplement are relatively small in size and easier to swallow, about 100 yuan for 180 tablets, which is moderately cost-effective in calcium citrate.
 
Due to the safe and effective test results and the design of low-dose calcium tablets, Calcium Citrate 1000mg was also recommended as the first choice in the third-party evaluation ConsumerLab in the United States.
 
肠胃健康的普通人群可选择更为便宜的GNC碳酸钙，其中表现最佳的是Calcium Plus 1000 with Magnesium & Vitamin D-3，钙量设计合理且物美价廉。这款钙剂的推荐用量同样是1000mg钙/日，每粒333mg钙，并含有适量镁和维生素D，价格约为80元180片。如非缺钙严重建议每日服用1-2片。
 
Calcium Plus 800, another well-known calcium carbonate, also contains magnesium and vitamin D, but it is high in vitamin D and is not recommended here.