Vitamins are nutrients that can be obtained through the diet or as dietary supplements. Getting the right amount of vitamins is necessary for your body to function properly.

You may not know that taking excess vitamins can cause a slew of health problems, including toxicity (hypervitaminosis). Vitamin overdose symptoms can include a skin rash, upset stomach, seizure, or stroke.

Can Excess Vitamins Harm Your Health?

Yes, taking excess vitamins can harm your health.

Vitamin supplements are often considered a harmless way to improve health. However, be mindful that there are risks associated with vitamins. This is especially important if you take high doses or take them for an extended period.

Serious risks associated with high doses of vitamins include the following:

• Increased mortality risk: Consistently high doses of vitamin E supplements (≥400 international units (UI)/day) are associated with an increased risk of death.
• Cancer risk: Studies have shown that high doses of vitamins A, B6, and B12 may increase lung cancer risk. Vitamin E supplementation in large amounts may cause cancer to recur after radiation treatment.
• Congenital disabilities: Taking high doses of vitamin A during pregnancy can cause abnormalities in the developing baby, including heart and brain damage.
• Fracture risk: Taking too much vitamin A or vitamin D can lower bone mineral density and increase the likelihood of bone fractures.

Fat-Soluble vs. Water-Soluble Vitamins

Vitamins are classified as either dissolvable in fat (fat-soluble) or dissolvable in water (water-soluble).

Fat-soluble vitamins include vitamins A, D, E, and K.

Water-soluble vitamins include all eight B vitamins and vitamin C.

Risks of Excess Fat-Soluble Vitamin Intake

These vitamins stay in the body longer and are more likely to build up in the body. This means that fat-soluble vitamins are more likely to cause toxicity.

Symptoms of too much vitamin A include:

• Skin peeling
• Liver problems
• Vision loss
• Increased pressure in the skull (intracranial hypertension)

Symptoms of too much vitamin D include:

• Excessive urination
• Seizures
• Coma
• Bone fractures

Symptoms of too much vitamin E include:

Risks of Excess Water-Soluble Vitamin Intake

Water-soluble vitamins are generally safer than fat-soluble vitamins because they don’t accumulate in the body. If you take too much of these vitamins, your body usually removes them through your urine.

Symptoms of a water-soluble vitamin overdose are often nonspecific, meaning they are vague and may not be immediately traced to the vitamin. These symptoms can include:

• Nausea
• Vomiting
• Diarrhea
• Skin rash

Who’s at Risk of Toxicity

Though anyone who takes vitamin supplements may experience vitamin toxicity, some populations are at greater risk. These include the following groups:

• Babies: Breastfed babies may develop excessive vitamin levels if their mothers take vitamin supplements. Infant formulas for premature babies often contain high amounts of vitamin D, which may cause toxicity if they are consumed for an extended length of time.
• Children: Children are at high risk of accidentally taking too much medicine. Many vitamins are marketed to look like candy or gummies, which makes them especially appealing to children.
• Pregnant people: Though vitamin deficiency during pregnancy can harm a developing baby, too much can also be dangerous. In fact, pregnant people in developed countries are more likely to have too much vitamin A than too little. High levels of vitamin A in the first trimester of pregnancy can cause heart or brain abnormalities in the baby or miscarriage.
• Older adults: Older adults may break down and eliminate medicines differently than younger people do. This means they may have higher or lower levels of vitamins in the body after a standard dose than a younger person would. For example, older adults may be more likely to experience cognitive problems if they take too much vitamin D.
• People taking multiple vitamins: You are more likely to take too much of a vitamin if you take a daily multivitamin or another vitamin combination plus a single-ingredient vitamin.

How Much of Each Vitamin Do I Need?

It’s important to remember that healthy, nonpregnant people who eat a balanced diet typically do not need to supplement with vitamins. In fact, research shows that most people who take vitamin supplements already get the recommended amounts of vitamins through food.

When determining how much of each vitamin you need, consider the amounts you consume in your diet plus any supplements you take (including multivitamins). Here’s what to aim for when it comes to a few heavy hitters:

• Vitamin A: Daily needs vary from 700 to 1300 micrograms (µg) per day, depending on gender and whether you’re pregnant or breastfeeding. Vitamin A is crucial for vision, bone growth, and a healthy immune system. Dietary sources include dairy, eggs, and fish.
• Vitamin B3: The recommended intake is 14 to 18 milligrams (mg) daily, depending on gender and pregnancy status. Vitamin B3, also known as niacin, is found in meats like chicken, beef, and fish. The body needs it to make energy.
• Vitamin C: Males should aim for 90 mg daily, while females need 75 to 120 mg daily, depending on pregnancy and lactation status. Vitamin C is an antioxidant that helps the body build collagen and break down protein. Humans don’t make vitamin C, so they must consume it through their diets or supplements. Fruits and vegetables are rich in vitamin C.
• Vitamin D: Most adults require 15 µg of vitamin D daily. The body makes vitamin D through exposure to sunlight. It is crucial for bone health. Some fish contain vitamin D, and many other foods are fortified with it.
• Vitamin E: Aim for 15 mg a day or 19 mg if you’re breastfeeding. Vitamin E is an antioxidant that boosts the immune system and protects against damage caused by free radicals. Dietary sources include nuts, seeds, and oils.

The Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine provides the following Recommended Dietary Allowances (RDAs) and Upper Limits (ULs) of vitamins for adults: