Here's Exactly How Much Vitamin D is Safe, as Man Hospitalized With Intoxication

A man in the UK was hospitalized after taking almost 400 times the daily recommended amount of vitamin D, highlighting once again the serious danger of taking unsafe doses of over-the-counter vitamins and supplements. “Vitamin D toxicity, also called hypervitaminosis D, is a rare but potentially serious condition that occurs when you have excessive amounts of vitamin D in your body,” says Katherine Zeratsky, RD, LD. “Vitamin D toxicity is usually caused by large doses of vitamin D supplements — not by diet or sun exposure. That’s because your body regulates the amount of vitamin D produced by sun exposure, and even fortified foods don’t contain large amounts of vitamin D.” 

So what happens when too many vitamin D supplements are taken? “The main consequence of vitamin D toxicity is a buildup of calcium in your blood (hypercalcemia), which can cause nausea and vomiting, weakness, and frequent urination,” Zeratsky says. “Vitamin D toxicity might progress to bone pain and kidney problems, such as the formation of calcium stones. Treatment includes stopping vitamin D intake and restricting dietary calcium. Your doctor might also prescribe intravenous fluids and medications, such as corticosteroids or bisphosphonates.”

Vitamin D—in the correct amount—is crucial for good health. “We have known for a long time that vitamin D is important for bone health,” says Marci A. Goolsby, MD. “One of the jobs of vitamin D is to help your gut absorb the calcium and phosphorus from your diet. These minerals in turn help build and maintain the strength of your bones. Low levels of vitamin D have been linked to stress fractures and other problems with the bones. But vitamin D has many other functions as well. I describe it to my patients as a delicate symphony of everything that goes on in your body. If one of the instruments — in this case, your vitamin D — is off, it can throw off the whole symphony.”

Here is the official recommended daily amount of vitamin D, according to the National Institutes of Health.

Life Stage                  Recommended Amount

Birth to 12 months      10 mcg (400 IU)

Children 1–13 years   15 mcg (600 IU)

Teens 14–18 years     15 mcg (600 IU)

Adults 19–70 years     15 mcg (600 IU)

Adults 71 years and older     20 mcg (800 IU)

Pregnant and breastfeeding teens and women     15 mcg (600 IU)

Vitamin D is not the only vitamin that can cause serious health issues if incorrectly dosed: Here are five other supplements that can make you sick if you don’t follow the recommended daily amounts. Read on—and to ensure your health and the health of others, don’t miss these Sure Signs You’ve Already Had COVID.

Young Woman Taking Yellow Fish Oil Pill.
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Adults should not take more than 2000 mg of vitamin C a day. 

The good: “Vitamin C, or ascorbic acid (AA), is first and foremost an electron donor,” says Bogdan Popa, MD. “This means it can directly donate electrons to function as an antioxidant. Functioning as an antioxidant allows it to neutralize harmful free radicals and act as a cofactor, also donating electrons to enzymes containing iron or copper. This donation is a critical step in keeping these enzymes ‘active.’ Enzymes that use vitamin C as a cofactor have widespread influence on our energy levels, structural integrity, and DNA. They are involved in maintaining methylation/demethylation balance (or turning on gene expression), making collagen, and furnishing L-carnitine and norepinephrine.” There is also fascinating research about the impact of vitamin C and fasting in treating some cancers

The bad: “Taking too much vitamin C can cause diarrhea, nausea, and stomach cramps,” says the NIH. “In people with a condition called hemochromatosis, which causes the body to store too much iron, high doses of vitamin C could worsen iron overload and damage body tissues. Vitamin C dietary supplements might interact with cancer treatments, such as chemotherapy and radiation therapy. It is not clear whether vitamin C might have the unwanted effect of protecting tumor cells from cancer treatments or whether it might help protect normal tissues from getting damaged.

Vitamin pills spilling from an open bottle
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Adults should not take more than 40 mg of zinc a day, which is the Tolerable Upper Intake Level. The recommended daily amount is 11 mg a day for men and 8 mg for women. 

The good: “Zinc is a trace mineral, meaning that the body only needs small amounts, and yet it is necessary for almost 100 enzymes to carry out vital chemical reactions,” says Harvard Health. “It is a major player in the creation of DNA, growth of cells, building proteins, healing damaged tissue, and supporting a healthy immune system. Because it helps cells to grow and multiply, adequate zinc is required during times of rapid growth, such as childhood, adolescence, and pregnancy. Zinc is also involved with the senses of taste and smell.”

The bad: “Yes, too much zinc can be harmful,” says the National Institutes of Health (NIH). “Signs of too much zinc include nausea, dizziness, headaches, upset stomach, vomiting, and loss of appetite. If you take too much zinc for a long time, you could have problems such as lower immunity, low levels of HDL (“good”) cholesterol, and low copper levels. Taking very high doses of supplemental zinc can reduce your body’s absorption of magnesium. Using large amounts of denture creams that contain zinc, well beyond what the label recommends, could lead to excessive zinc intake and copper deficiency. This can cause neurological problems, including loss of coordination, numbness, and weakness in the arms, legs, and feet.”

assortment of red pills and capsules of iron supplements
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The recommended daily amount of iron for adults is 8mg for men and 18 mg for women, which goes up to 27 mg for pregnant women.

The good: “Iron is an essential element for blood production,” says UCSF Health. “About 70 percent of your body’s iron is found in the red blood cells of your blood called hemoglobin and in muscle cells called myoglobin. Hemoglobin is essential for transferring oxygen in your blood from the lungs to the tissues. Myoglobin, in muscle cells, accepts, stores, transports and releases oxygen. About 6 percent of body iron is a component of certain proteins, essential for respiration and energy metabolism, and as a component of enzymes involved in the synthesis of collagen and some neurotransmitters. Iron also is needed for proper immune function.”

The bad: “Although iron ingestion is no longer the leading cause of poisoning deaths, it is not uncommon and can be a potentially fatal toxicologic emergency,” says University of Utah Health. In 2020, 4688 single cases of iron ingestion (as iron or iron salt formulations) were reported to US poison centers, with 2004 of those cases being in children under the age of 5 years. Also in 2020, there were about 8800 single cases of ingestion of a multivitamin formulation containing iron. Iron can cause direct injury to gastrointestinal mucosa, vasodilation, and impairment of cellular metabolism in the heart, liver, and central nervous system by disrupting oxidative phosphorylation and formation of free radicals. The toxicity of iron depends on the amount of elemental iron ingested, and elemental iron amounts vary between products… Patients who ingest 20-60 mg/kg of elemental iron may develop nausea and vomiting but are at a low-risk for severe toxicity, while > 60 mg/kg is associated with a high-risk for severe toxicity and death.”

woman taking fish oil
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The recommended daily amount of omega-3 according to the NIH is 1.6 g for men and 1.1 g for women, going up to 1.4 g during pregnancy.

The good: “​​For heart health, you may have heard a lot of talk about the benefits of fish oil supplements,” says Penn Health. “While studies have shown that fish oil supplements may provide some benefits to some people with some heart health issues, the real source of these cardiovascular health benefits is from a family of polyunsaturated fats called omega-3 fatty acids. Here’s what you should know about fish oil, omega-3 fatty acids, and heart disease… The most consistent evidence for omega-3s and heart health is their ability to lower triglyceride levels. Triglycerides are a type of fat found in your blood and are stored as body fat. High levels of triglycerides have been linked with fatty build-up in the artery walls, which increases your risk of heart attack and stroke.”

The bad: “Very high doses of fish oil may suppress the immune system as well as have blood-thinning effects,” says Tod Cooperman, MD. “In people taking highly concentrated prescription fish oil, elevations in “bad” LDL cholesterol and certain liver enzymes, and an increase in episodes of atrial fibrillation or atrial flutter in people who already have this heart rhythm disorder, have been reported. Be aware that cod and other fish liver oils can be high in vitamins A and D, which can be toxic in high doses. Too much vitamin A, for example, can cause liver damage. Too much vitamin D can cause hypercalcemia (too much calcium in the blood), resulting in symptoms such as constipation, confusion, weakness and loss of appetite. While fish oil is not believed to adversely affect blood sugar levels in people with diabetes, one study found that taking a large amount of krill oil which contained relatively modest amounts of EPA + DHA (230 mg and 154 mg, respectively) was shown to significantly reduce insulin sensitivity in overweight, middle-aged men, which could potentially increase the risk of the risk of diabetes and cardiovascular disease.”

folic acid
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The recommended daily amount for adults is 400 mcg of dietary folate equivalents (DFE), going up to 600 mcg for pregnant women.

The good: “Folate is the natural form of vitamin B9, water-soluble and naturally found in many foods,” says Harvard Health. “It is also added to foods and sold as a supplement in the form of folic acid; this form is actually better absorbed than that from food sources—85% vs. 50%, respectively. Folate helps to form DNA and RNA and is involved in protein metabolism. It plays a key role in breaking down homocysteine, an amino acid that can exert harmful effects in the body if it is present in high amounts. Folate is also needed to produce healthy red blood cells and is critical during periods of rapid growth, such as during pregnancy and fetal development.”

The bad: “Unfortunately, many prenatal supplements provide 800 mcg or more of folic acid — double the recommended amount from a supplement,” says Dr. Cooperman. “That’s not all. Folic acid is absorbed much better (about 70% better) than folate from foods. This means that a prenatal supplement with 800 mcg of folic acid gives you the equivalent of 1,360 mcg DFE of folate. On top of this, many manufacturers put in extra folic acid (30% or more is not uncommon), so it’s quite possible that your supplement which lists 800 mcg of folate from folic acid is giving you the equivalent of about 1,800 mcg of folate… Prolonged intake of excessive folic acid can cause kidney damage and can complicate the diagnosis of vitamin B-12 deficiency (folic acid supplementation can mask a symptom of vitamin B-12 deficiency). Of particular concern to pregnant women is that excessively high blood levels of folate (>59 nmol/L) in their blood was found to be associated with an approximate twofold increased risk of autism in their children according to an observational study in Baltimore in which 10% of women exceeded this level.”

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