Vitamin Overdose: 5 Dietary Supplements That Can Do You More Harm Than Good

Not always a quantity of vitamins means a greater benefit for the body. In some cases, too much of a dietary supplement such as vitamin D, B6 or A, iron or calcium can do us more harm than good.

When too many vitamins can be bad – Photo Shutterstock

Exceeding healthy amounts can have far more serious consequences than simple indigestion.

We definitely want people to be cautious with (fat-soluble vitamins) because they will build up in the system, and those are the ones that can cause more toxicity in excess.”Dr. Wendolyn Gozansky, a geriatrician and director of quality at Kaiser Permanente, told AARP, as quoted by the New York Post.

There are two categories of vitamins: water-soluble and fat-soluble. Water-soluble vitamins, such as vitamin C and B vitamins (such as folate, biotin, thiamin, niacin, and others), are not easily retained in the body and can be eliminated in the urine, according to the National Institutes of Health. On the other hand, fat-soluble vitamins are easier to store, meaning they can build up and cause toxicity.

Healthy people don't need nutritional supplements, but out of a desire to be healthy and stay fit, we're tempted to take vitamins even when we shouldn't.

Nearly 60 percent of adults over the age of 20 reported taking vitamins or supplements in the past 30 days, according to the CDC. Use was higher among women (63%) than men (51%).

Although multivitamins are generally beneficial, and an occasional supplement probably won't do much harm, some vitamins or minerals taken in excess can have negative effects on the body. More specifically: vitamin D, vitamin B6, vitamin A, iron and calcium in excess can cause discomfort


Excess calcium can be harmful, although it is essential in adequate amounts. About 98% of calcium is stored in the bones and is crucial for bone health and other vital functions such as the contraction of blood vessels and blood clotting.

According to the CDC, calcium is the most abundant mineral in the body, but that doesn't mean it should be consumed in excess.

Overdose, usually from supplements, can cause symptoms such as abdominal pain, nausea, and even kidney stones and heart problems.

The recommended daily dose is 1,000 to 1,200 mg, depending on age and sex. Dairy products such as milk and yogurt can help to reach this level.

Anything over 2,200 milligrams a day can cause stomach problems or predispose people to kidney stones“said Dr. Wendolyn Gozansky.


And excess iron can be harmful. Although a low level of this mineral can lead to anemia, most people do not have this problem.

According to the World Health Organization (WHO), approximately 1.62 billion people globally experience iron deficiency, which is approximately 24.8% of the world's population.

Iron can be obtained from foods such as red meat, fortified cereals, oysters, lentils and spinach. In some cases, such as during pregnancy, iron supplementation may be necessary.

Eating too much iron can cause serious problems, including damage to major organs, in addition to nausea, vomiting, and diarrhea. The CDC recommends between 8 and 18 mg of iron per day, depending on age and gender.

Too much iron can actually cause liver and heart problems because it will be deposited in the tissuesGozansky said.

Vitamin A

You may be familiar with the cosmetic form of vitamin A, retinol, but this vitamin has much wider roles in the body than fighting wrinkles and skin aging. Vitamin A, a fat-soluble vitamin, can cause liver toxicity when consumed in excess.

You may have some acute symptoms such as nausea, vomiting, dizziness, blurred vision”Dr. Matthew Farrell, a family medicine physician at Ohio State University Wexner Medical Center, told AARP.

Other signs may include severe headaches and muscle or coordination difficulties.

In the most extreme cases, an overdose of vitamin A can cause coma or even death, although most people recover with appropriate intervention.

Vitamin D

Vitamin D, also known as “sunshine vitamin“, is special because, in addition to the fact that it can be consumed from food, our body also produces it through exposure to the sun.

According to the CDC, it is one of the most popular supplements, especially since it plays an important role in strengthening the immune system. Getting adequate vitamin D is essential for bone, kidney and muscle health, but too much can cause serious problems.

We don't want people to take too much vitamin D because it can actually cause problems with high blood calcium levels as well.”Gozansky explained.

A 2022 case study shows how a British man battled the effects of a vitamin D overdose after taking 375 times the recommended daily allowance, or 150,000 IU. He experienced severe symptoms such as nausea, vomiting, dry mouth, weight loss and diarrhea, even ending up with kidney problems.

In another similar case, an 89-year-old man died of hypercalcemia, resulting from an overdose of vitamin D. At the time, the medical examiner even noted in his report: “In my opinion, there is a risk that future deaths will occur if action is not taken“, according to the cited source.

The recommended daily intake for the average person is 600 to 800 IU, and this can be obtained through exposure to the sun for 5 to 30 minutes, or by eating fatty fish, dairy products, and vitamin D-fortified cereals.

Vitamin B6

Vitamin B6 can be dangerous in large doses, even if it is soluble in water. Taking more than 250 mg per day can cause nerve damage and pain, according to the AARP. Eating foods such as chickpeas, liver, tuna and salmon can provide the daily requirement of 1.3 to 1.7 mg, depending on age.