Vitamins and minerals are essential for good health, but there’s a reliable rule that applies to everything we consume: More isn’t always better, meaning it’s possible to take too much of certain vitamin supplements.

People taking vitamin supplements must be especially careful to avoid getting too much of a good thing—and, according to a study published in JAMA Network, that applies to a whole lot of us. Approximately half of all American adults take at least one dietary supplement, noted the authors, and those working in the medical industry are no exception. Roughly 28% of US nurses report using at least four dietary supplements.

Other estimates are even higher: According to the Council for Responsible Nutrition, a record-high 77% of Americans take at least one dietary supplement. The number is even higher—81%—in adults aged 35-54 years. 

While taking too many vitamin supplements doesn’t always pose a serious threat to health, it can result in adverse health outcomes in some cases. Here’s a breakdown of the vitamins that deserve your attention and the consequences of overdoing it, according to the latest research.

Why you should exercise caution

If you’re eating a balanced diet and don’t have any underlying health conditions, you’re likely getting all the vitamins and nutrients you need from food. The vitamins should be supplementing something that’s missing from your diet. If your nutrition is bad or you have a condition or disease that prevents your body from absorbing certain nutrients, then yes—you need to take supplements. But if your gut is working well and you’re eating a balanced diet, you’re probably getting all the nutrients your body needs and shouldn’t have to take a supplement. If you do take supplements and ingest more of a vitamin or mineral than your body needs, the excess will either be excreted or stored, depending on the type of vitamin. If the vitamin is water-soluble, it can be flushed out of the system via urination. However, if it is a fat-soluble vitamin, it will be stored in fat, and an accumulation of fat-soluble vitamins is more likely to result in health problems. Of note, for elderly people or those with kidney problems, even water-soluble vitamins may also stick around and can accumulate to toxic levels.

Fat-soluble vitamins

The fat-soluble vitamins A, D, and E are worth watching out for. While symptoms like nausea, vomiting, diarrhea, and rash are common with any case of chronic overdosing, there are more specific symptoms for each vitamin.

Acute vitamin A toxicity can result in hair loss, weight loss, fatigue, insomnia, bone fractures, hyperlipidemia (high levels of blood fat), hypercalcemia (high blood calcium content), anemia, and other symptoms. Government guidance from the National Academy of Medicine (NAM) states that adult males should aim to consume 900 μg (micrograms) of vitamin A daily, but no more, and adult females should aim to consume 700 μg.

Vitamin E toxicity can involve gastric distress, abdominal cramps, easy bruising and bleeding, inhibition of blood platelet aggregation, and increased risk of hemorrhagic stroke. Adults of either sex should aim to consume roughly 15 mg of vitamin E daily.

The symptoms of vitamin D toxicity are similar to those of hypercalcemia (elevated blood calcium) and can include muscle weakness, bone pain, constipation, abdominal cramps, polydipsia (excessive thirst), polyuria (excessive urination), backache, hypertension, and cardiac irregularities.

While rare, a recent case of vitamin D overdose was detailed in an article published in the Canadian Medical Association Journal. A 54-year-old man who had just spent 2 weeks sunbathing for 6-8 hours per day while on vacation was taken to a nephrology clinic for suspected acute kidney injury. His blood levels for waste products (creatinine) and calcium were consistent with kidney failure. Doctors subsequently discovered that the man had been prescribed high doses of vitamin D by a naturopathic specialist, and that he had been taking 8-12 drops of vitamin D daily for the past 2.5 years, for a total daily dose of 8,000-12,000 IU. The patient was told to stop taking all vitamin D supplements and avoid calcium-rich foods. After a year of this treatment, the man’s calcium and vitamin D levels returned to normal—but he was left with moderate chronic kidney disease. Scientific study indicates that adults should get 15 mcg (roughly 600 IU) of vitamin D daily, and 20 mcg for those 70 years or older.

Water-soluble vitamins

While excess levels of water-soluble vitamins are typically excreted from the body, they can still accumulate to toxic levels. Vitamin C toxicity can result in abdominal pain, diarrhea, blood disorders, dental decalcification, increased estrogen levels, and occult rectal bleeding. Male adults should aim to consume no more than 90 mg of vitamin C daily, and that female adults, 75 mg.

We should also pay attention to our intake of vitamin B6 (pyridoxine). Too much can result in neurological symptoms, like tingling in the feet and numbness.


The best advice for the general public is simply to eat a normal, balanced diet and, with rare exceptions, avoid the use of all supplements.


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