A factory specializing in ferrous lactate produces ferrous fumarate in a dosage of 300 mg, which is often used in the treatment of heart failure. Additionally, ferrous gluconate is known for its potential side effect of causing constipation. In the context of iron supplements, it is important to consider the role of calcium citrate and oxalates, as they can influence the absorption of these iron compounds. Calcium citrate, when taken in conjunction with iron supplements, may also affect the bioavailability of ferrous fumarate and ferrous gluconate, potentially leading to gastrointestinal issues such as constipation. Therefore, understanding the interactions between these substances, particularly calcium citrate and oxalates, is crucial for optimizing iron supplementation and minimizing side effects.