April 20, 2023

Vitamin A Toxicity: How Much Vitamin A Is Too Much?

Vitamin A toxicity can cause drug interactions, fetal development issues and other side effects

Person with blue shirt is holding vitamin bottle and other hand is holding one vitamin.

Vitamin A is important for visual health. It also contributes to healthy skin and hair and boosts your immunity. If you’re not getting enough, you can develop symptoms like night blindness, dry, scaly skin around your eyes, coarse hair and respiratory infections.

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Vitamin A deficiencies are more common in some parts of the world than others. This is because of many factors, including food insecurity, frequent gastrointestinal infections caused by poor water sanitation, inadequate healthcare access and a high prevalence of measles, which can cause vitamin A to be lost in urine.

While it’s important to avoid a vitamin A deficiency, it’s equally important to make sure you aren’t overdoing it on supplements. We’ll walk you through how much vitamin A you need to feel your best — and what happens when you take too much.

What is vitamin A?

It’s best to get vitamin A from fruits and vegetables that contain carotenoids. In addition to orange-colored vegetables and fruit — carrots, sweet potatoes, squash and papayas — you also need lycopene, astaxanthin, zeaxanthin and lutein. You can find these carotenoids in red and yellow-orange fruits and vegetables, as well as leafy greens, eggs, shrimp and salmon. And don’t forget watermelon, guava, pink grapefruit and tomatoes!

It’s important to get as many vitamins and nutrients as you can from your food. “However, widespread changes in farming practices mean a lower nutrient content in our fruits and vegetables,” cautions functional medicine specialist Melissa Young, MD. “Many people still benefit from having their nutrient levels assessed and taking a high-quality daily multivitamin.”

While a supplement may be the right choice, dosing matters. That’s because there is such a thing as too much vitamin A.

Too much vitamin A symptoms

Fat-soluble vitamins like vitamin A can lead to toxicity because your body doesn’t excrete any excess — it stores it. Vitamin A’s presence in so many different supplements compounds the problem.

Vitamin A doses are measured in micrograms of retinol activity equivalents (mcg RAE). This measurement is to account for the different properties of retinol and provitamin A carotenoids. Depending on your age, sex and whether or not you’re pregnant or lactating, your recommended daily amount is between 500 mcg REA and 1,800 mcg of vitamin A per day REA.

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The recommended daily allowance (RDA) for adult men and people assigned male at birth (AMAB) is 900 MCG REA, or 3,000 international units (IU). For adult women and people assigned female at birth (AFAB) the RDA is 700 mcg RAE, or 2,330 (IU). For all adults, the Tolerable Upper Intake Level (UL) — the most vitamin A one can take without experiencing negative health effects — is 3,000 mcg RAE, or 10,000 IU.

“Patients who take a variety of supplements are getting much more vitamin A than they should,” says Dr. Young. Some supplements may include two forms of vitamin A — retinyl acetate and mixed carotenoids — which she says is a good combination for most people. The exception: People who smoke. That’s because clinical trials show that beta-carotene supplements were associated with an increased risk of lung cancer in people who smoke. Smokers or former smokers should not take beta-carotene supplements.

There are two different kinds of vitamin A toxicity: acute and chronic.

Acute vitamin A toxicity symptoms

Acute vitamin A toxicity happens when somebody — usually a child — accidentally ingests a megadose of vitamin A. Common symptoms include:

  • Headache.
  • Rash, which may cause the affected skin to peel later.
  • Drowsiness.
  • Irritability.
  • Stomach pain, nausea and vomiting.

In acute vitamin A toxicity cases, symptoms should resolve over time. Still, if an individual (especially a child) is experiencing these symptoms, you should call Poison Control, and, if directed, go to the nearest emergency room.

Chronic vitamin A toxicity symptoms

Chronic vitamin A toxicity happens when a person takes excessive doses of vitamin A (10,000 IU or more) per day over a prolonged period. The symptoms are more subtle and harder to distinguish from other conditions. They include:

  • Severe headaches and pressure in your skull (idiopathic intracranial hypertension).
  • Hair issues like sparse, coarse hair and alopecia of your eyebrows.
  • Skin issues, like dry, rough, itchy skin (pruritus) and cracked lips.
  • Weakness and susceptibility to fractures.
  • Enlarged liver (hepatomegaly) or spleen (splenomegaly).
  • Children may experience loss of appetite (anorexia), joint pain (arthralgia) and excessive bone growth (cortical hyperostosis). Vitamin A toxicity can also cause “failure to thrive,” which — while not a good thing — sounds scarier than it is. It basically means your child’s growth has either slowed or stopped.

Once you stop taking the supplement, the symptoms of chronic vitamin A toxicity usually take between one and four weeks to resolve.

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There’s one very important exception to that rule: Vitamin A is teratogenic, which means it can cause fetal development issues. Once those malformations occur, they can’t be reversed. For that reason, pregnant people — and people who may become pregnant — shouldn’t take excessive doses of vitamin A.

What to do if you’ve taken too much

If you suspect somebody has acute vitamin A toxicity — meaning they ingested a megadose of vitamin A — you should call Poison Control at 1.800.222.1222 for immediate assistance.

If you’re concerned that you or a loved one may be experiencing the effects of chronic vitamin A toxicity, you should schedule an appointment with a healthcare provider. They’ll review your medication and supplements, as well as conduct blood tests, to determine what’s causing your symptoms.

Takeaway

Avoiding vitamin A deficiency is important … but it’s also important to avoid vitamin A toxicity. So, before you pick up those pills or gummies, speak with a doctor. They can let you know if you really need to be taking a supplement — and determine the right dose for your particular situation.

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