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Last updated: Oct 27, 2021
4 min read

Vitamin A toxicity: what happens if you take too much vitamin A?

Disclaimer

If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

Vitamin A is one of the essential micronutrients and has many important functions in the body, including helping your eyesight and immune system, and helping a fetus develop during pregnancy. You may think there could be no harm in adding extra vitamin A to your day, considering how beneficial this nutrient is. But, sometimes, too much of a good thing can cause problems. 

This article covers how vitamin A toxicity develops, the symptoms, and treatment. 

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What is vitamin A?

Vitamin A, is an essential nutrient used for cell division, growth, vision, and immune function. Vitamin A is naturally found in a wide variety of foods. The body converts vitamin A into its active form from either preformed vitamin A or provitamin A. 

Preformed vitamin A, known as retinoids (retinal, retinoic acid, isotretinoin, and retinol), is found in animal foods like:

  • Animal liver
  • Meat
  • Dairy products
  • Eggs
  • Fish oils

Provitamin A, known as carotenoids (beta-carotene and alpha-carotene), provides the orange pigment in plant foods, such as:

  • Carrots
  • Cantaloupe
  • Green leafy vegetables
  • Red bell pepper
  • Sweet potatoes
  • Apricots
  • Fortified cereal

The recommended dietary allowance (RDA), which describes the recommended daily intake of vitamin A, is around 700–900 micrograms (mcg) or 2,300-3000 IU (Chea, 2021).

Can you have too much vitamin A?

Vitamin A is a fat-soluble vitamin, which means it’s absorbed with fat and stored in fat tissue, unlike water-soluble vitamins that leave the body in urine. Large amounts of vitamin A can lead to too much of the nutrient in the body and reach toxic levels, a condition called hypervitaminosis A. 

Vitamin A toxicity can be an acute or a chronic condition. It’s uncommon for vitamin A toxicity to develop through diet alone. Typically, when levels of vitamin A become too high, it’s caused by large doses of dietary supplements.

Vitamin A toxicity signs and symptoms

Acute vitamin A toxicity may develop after one large dose of vitamin A of greater than 25,000 IU per kilogram. Chronic vitamin A toxicity may develop after taking vitamin A supplements of greater than 4,000 IU per kilogram per day for 6–15 months (Chea, 2021). 

Acute vitamin A toxicity symptoms

Some of the symptoms of acute vitamin A toxicity include (Chea, 2021):

  • Nausea and vomiting
  • Diarrhea
  • Dizziness
  • Drowsiness and fatigue
  • Intracranial pressure and headaches
  • Skin irritation—redness, itching, and peeling 

Chronic vitamin A toxicity symptoms

The following are signs and symptoms of chronic vitamin A toxicity (Chea, 2021):

  • Fever
  • Headache
  • Fatigue and tired feeling
  • Weight loss and anorexia
  • Digestive problems
  • Enlarged liver and spleen (hepatosplenomegaly)
  • Anemia
  • High levels of calcium in the blood
  • Swelling
  • Increased need to urinate at night (nocturia)
  • Joint and bone pain
  • Yellow-colored skin
  • Dry skin
  • Hair loss (alopecia)
  • Elevated triglycerides and cholesterol levels
  • Sensitivity to light

Complications

Prolonged high levels of vitamin A can lead to some complications, like (Olson, 2021):

  • Liver damage: Vitamin A is stored in the liver. Excess vitamin A builds up in the liver and may cause liver disease (cirrhosis).
  • Osteoporosis: High levels of vitamin A may speed up bone loss and increase the risk for osteoporosis and broken bones. 
  • Hypercalcemia: As bones are broken down, calcium is released from bones, leading to excess calcium moving around in the bloodstream. Symptoms of hypercalcemia include bone pain, muscle aches, forgetfulness, and digestive problems.
  • Kidney damage: Excess calcium and vitamin A could lead to kidney damage and the development of chronic kidney disease.

Pregnancy and vitamin A

Vitamin A is essential during pregnancy to protect your health and support the growing baby, but too much vitamin A could lead to complications during pregnancy, like congenital disabilities (Olson, 2021). 

Too much vitamin A could impact the baby’s skull, eyes, lungs, and heart. Consuming a balanced diet and a prenatal vitamin as recommended by your healthcare provider should be enough to provide for your vitamin A needs while pregnant, and you shouldn’t need additional supplementation beyond that.

Many skincare products contain vitamin A. Since vitamin A is known to cause birth defects, ethically, researchers aren’t able to do studies to determine if there are side effects of using skincare products with vitamin A during pregnancy. Because of this, it’s recommended for women to avoid using topical skincare products with retinoids, like:

  • Tretinoin
  • Isotretinoin
  • Retinoic acid
  • Retinal
  • Serum retinol

If you were previously using these products to help manage acne or aging skin, talk with your healthcare provider about other options you can use while pregnant.

How is vitamin A toxicity diagnosed?

Your healthcare provider will start by gathering information about your medical history, diet, supplements, and symptoms. They will perform a physical exam to assess your symptoms and check for other potential causes. 

If your healthcare provider suspects hypervitaminosis A, they will order lab work and a blood draw to check the levels of vitamin A in your blood. High levels of vitamin A circulating the body are used to diagnose toxicity.

Vitamin A toxicity treatment

Usually, vitamin A toxicity is caused by high-dose vitamin A supplements. So, the first line of treatment is to stop taking any dietary supplements that contain vitamin A. 

Most people will notice improvements in their symptoms and have a full recovery within a few weeks of stopping supplementation. 

For severe cases of chronic toxicity, it could take longer for symptoms to go away. If kidney, liver, or bone complications develop, your healthcare provider will help you determine a treatment plan for those complications. 

Preventing hypervitaminosis A

The best way to prevent vitamin A toxicity is to focus on reaching your vitamin A requirements through your diet. With good access to a variety of foods, most people are able to meet their needs through their diet and prevent a vitamin A deficiency. 

If you’re looking for a supplement, consider simply taking a daily multivitamin because these typically contain around 100% of your daily vitamin A needs and don’t typically provide too large of a dose when taken as directed—but of course, check the label to make sure. If you have any questions about your micronutrient needs, talk with your healthcare provider. They can help you determine if any supplements are right for you and help you find the cause of any symptoms you’re experiencing.

References

  1. Chea, E. P., Lopez, M. J., & Milstein, H. (2021). Vitamin A. [Updated 2021 Jul 25]. In: StatPearls [Internet]. Retrieved on Oct. 18, 2021 from https://www.ncbi.nlm.nih.gov/books/NBK482362/
  2. Olson, J. M., Ameer, M. A., & Goyal, A. (2021). Vitamin A toxicity. [Updated 2021 Aug 14]. In: StatPearls [Internet]. Retrieved on Oct. 18, 2021 from https://www.ncbi.nlm.nih.gov/books/NBK532916/