Namely, as Health reports, certain combinations can reduce absorption or cause side effects. Taking calcium with other minerals like iron is not a good idea. "Calcium and zinc can block the absorption of iron supplements because they compete for absorption in the intestines. This is especially important for people who have an iron deficiency and need additional iron to improve anemia," said Jennifer Warren, medical director of Mochi Health. Since iron and calcium compete for absorption in the digestive tract, taking them together can reduce their effectiveness by decreasing the amount of these nutrients your body absorbs. To ensure the best absorption, take iron only in the morning with water or citrus juice, as vitamin C can aid iron absorption, and avoid other mineral supplements for at least two hours. If iron supplements cause nausea when taken on an empty stomach, you can take them with a small amount of food. Calcium should also be taken alone to optimize absorption. Like iron, calcium competes for absorption with other minerals, such as zinc. "Calcium and zinc will compete for absorption in the intestines, so taking them together can reduce the amount you absorb from each," said Vivek Lal, director of clinical innovation at the Heersink Institute for Biomedical Innovation. Zinc supports immune function and healing, while calcium helps fill dietary gaps to meet daily needs for bone health. Poor absorption due to nutrient competition affects these benefits. A simple routine is to take calcium supplements with meals and separate zinc from calcium-rich meals or supplements. It should be noted that while certain forms of calcium, such as calcium citrate, can be taken with or without food, other forms, like calcium carbonate, should be taken with meals. Copper and zinc compete for absorption in the small intestine. These minerals compete for absorption because they share similar transporters in their absorption pathways. Although copper and zinc compete for absorption, research suggests that problems usually arise from taking very high doses of zinc. Studies show that long-term intake of 60 milligrams or more of zinc per day can impair copper absorption and reduce blood copper levels. Copper deficiency can cause health issues like anemia and muscle weakness. It is important to stay below the tolerable upper intake level (UL) for zinc, which is set at 40 milligrams per day for adults. Space out the dosing of these minerals throughout the day or opt for a balanced mineral or multivitamin supplement containing lower doses of zinc and copper. Platelets are small blood cells that help blood clot to prevent bleeding. "Ginkgo and high doses of fish oil inhibit platelet function, so taking them together can increase the risk of bleeding due to blood thinning," explained Lal. This is especially important for people taking blood-thinning medications like warfarin. The same caution applies to other blood-thinning supplements like garlic, ginger, turmeric, and ginseng. Namely, taking high doses of supplements with blood-thinning properties can be dangerous, especially for individuals already on blood-thinning medications. Additionally, it is not a good idea to take blood-thinning supplements before planned surgery, as this can increase the risk of bleeding. To protect yourself, Lal recommended avoiding combining these supplements, considering lower or alternative dosing, and reviewing your regimen with a doctor, especially before any surgical procedure.