Once the human body uses the vitamins and minerals it needs, the rest is excreted or stored. There are some supplements that can cause harm, so you should know what you're taking. There are water-soluble and fat-soluble vitamins. Too much vitamin C or zinc can cause nausea, diarrhea, and stomach cramps.
Too much selenium can cause hair loss, gastrointestinal disorders, fatigue, and minor nerve damage. Any ingredient in a multivitamin supplement can be toxic in large amounts, but the most serious risk comes from iron or calcium. Manufacturers can add vitamins, minerals, and other supplement ingredients to the foods you eat, especially cereals and breakfast drinks. As a result, you may be eating more of these ingredients than you think, and more isn't better.
Taking more than you need costs more and could also increase your risk of side effects. For example, too much vitamin A can cause headaches and liver damage, reduce bone strength, and cause birth defects. Too much iron causes nausea and vomiting and can damage the liver and other organs. Keeping your daily intake of vitamin A close to the recommended amounts is the safest option, since taking more chronically can be harmful.
In addition to vitamin K, which has a low potential for toxicity, the remaining three fat-soluble vitamins have a fixed dose because of their potential to cause harm at high doses. Vitamins A and D can cause symptoms when large doses are taken every day, but a single large dose of these vitamins is rarely harmful. Tell your healthcare providers (including doctors, dentists, pharmacists, and dietitians) about any dietary supplements you are taking. When consumed naturally through food, these nutrients are unlikely to cause harm, even if consumed in large quantities.
As an alternative, taking high doses of non-synthetic vitamin K seems to be relatively safe, which is why a maximum intake level (UL) for this nutrient has not been established (. Several independent organizations provide quality tests and allow products that pass them to carry a quality assurance seal that indicates that the product has been properly manufactured, contains the ingredients listed on the label, and does not contain harmful levels of contaminants.