Hypervitaminosis A – Symptoms, Effects, Prevention, Treatment

Hypervitaminosis A is a condition that occurs when the body contains the highest levels of vitamin A. The consumption of fortified foods is likely to bring with it the excessive vitamin A which can potentially damage the overall bone metabolism of fat-soluble vitamins. The hypervitaminosis A symptoms are extremely toxic. The vitamin A hypervitaminosis has long been occurring throughout the human history. The foods that produce the highest levels of vitamin A are animal’s liver and fish. Sometimes, people also consume supplements and prescription medications which can bring along toxic effects of vitamin A. In this article we are going to discuss the probable effects of consuming too much vitamin A and what we can do to prevent it.

Hypervitaminosis A


  • The study of fossilized skeleton of ancient humans suggests the occurrence of vitamin A toxicity. The early humans had suffered from bone abnormalities which may have possible occurred due to hypervitaminosis A.
  • The Inuit people have long been aware of the toxicity of vitamin A.
  • Gerrit de Veer, a European explorer in 1597, mentioned in his diary that his men got critically ill when they ate polar bear liver.
  • Douglas Mawson and Xavier Mertz were the Antarctic explorers. They had consumed sled dogs’ livers in 1913 and as a result Mertz died. Researchers are however aren’t sure what may have caused Mertz’s death.
hypervitaminosis A
Cod Liver Oil is probably the most toxic source of Vitamin A.

Most Probable Causes of Hypervitaminosis A

Since you probably know that the hypervitaminosis A is mainly caused by consuming too much vitamin A there is a genetic variance in resisting vitamin A intake. The hypervitaminosis is particularly common in children but since they are highly sensitive to the excessive vitamin A intake their body shows toxic effects far too early.

Different Types of Vitamin A?

  • Provitamin Carotenoids such as beta carotene are almost entirely non-toxic. They are least likely to produce any poisonous symptoms for their conversion to retinol is extremely regulated. Not a single vitamin A toxic case has ever been reported to date which involves overconsumption of provitamin carotenoids. However, the excessive intake of beta carotene can lead to carotenosis but these are harmless and it only changes the skin color to orange.
  • The performed vitamin A usually found in the liver, is highly efficient in that it produces pathologic condition. The liver seems to contain as much as 70 – 90% vitamin A which means if you consume the entire liver, your body likely absorbs 90% of vitamin A. In this case the overconsumption will lead to terrible toxic effects.

Causes of Vitamin A Toxicity?

  • The chief component of producing high levels of vitamin A is a Animals that particularly contain the toxic liver are polar bear, walrus, bearded seal, and moose. While the liver of these animals isn’t really deadly it does produce toxic effects and so it is dangerous feast to feed on. It is highly not recommended for consumption.
  • Sometimes it happens that people take supplements more than they are recommended, the over-dosage likely leads to toxic effects. Cod liver oil is thought to contain pretty much high levels of vitamin A.
  • There are medicines that seem to contain high level of vitamin A. Doctors prescribe these medicines may be to prevent other diseases but their consumption over a certain period of time likely causes hypervitaminosis A.

Different Types of Toxicity?

  • Acute Toxicity is most likely to develop and persist for a few days but it doesn’t lead to any serious toxicity.
  • Chronic Toxicity is far more problematic than the acute toxicity. It is mainly caused when you consume perhaps too much of vitamin A over a long period of time—say months or years. People who continuously take 25,000 UI of vitamin A for 180 days or 100,000 UI for 200 days are particularly vulnerable to toxicity.

Signs & Symptoms of Hypervitaminosis A

Softening of the Skull BoneBlurred Vision Bone Swelling
Changes in consciousness Decreased Appetite Dizziness
Double VisionHeadacheHeart Valve Calcification
Gastric mucosal calcinosisIrritabilityDrowsiness
Skin and hair changesHigher sensitivity to sunlightSkin peeling, itching
Poor weight gain Hair LossNausea
HypercalcemiaBulging Fontanelle Cracking at corners of the mouth (mouth ulcers)
Spontaneous fracturePremature epiphyseal closureOily skin and hair (seborrhea)
Yellow discoloration of the skin (aurantiasis cutis)VomitingVision changes
Bulging EyeballsCracked FingernailsRespiratory Infection

Absorption and Storage

Absorption of Vitamin A Reserves

If you eat a polar bear liver your body will probably absorb and consume 70 to 90% of the performed vitamin A.

Storage of Vitamin A Reserves

The liver is probably the only organ which contains 80 to 90% of the entire body’s vitamin A. The distribution of vitamin A reserves within the liver is like 10 – 20% stored in hepatocytes and 80 – 90% in hepatic stellate cells. Your body fats can also store vitamin A reserves so as your kidney and lung.

Probable Effects of Hypervitaminosis A

There are two major effects that are likely to occur as a result of vitamin A overdose.

Increased Bone Turnover: The increased bone turnover is most likely to occur when retinoic acid overcomes the osteoblast activity and producing osteoclast formation in vitro. It indeed suppresses bone formation while at the same time enhancing the bone resorption. The increased bone turnover also casts a significant influence on particular nuclear receptors which exist in nearly every cell.

Furthermore, studies indicate that the altered bone turnover is primarily responsible for producing several hypervitaminosis A effects including hypercalcemia, radiographic changes, and osteoporosis.

Fat-soluble Vitamins: The excess quantity of vitamin A is reported to affect other fat-soluble vitamins such as vitamins D, E, and K. The toxic effects of hypervitaminosis A is most likely to alter the vitamin D metabolism. According to researchers, the synergistic and antagonistic interactions occur as a result of vitamin A overdose.

Hypervitaminosis A Diagnosis

The diagnosis of vitamin A level is rather complicated. The toxicity level in a person’s body who has consumed too much vitamin A may not reflect on the accurate toxicity for the retinol concentrations are non-sensitive indicators. The range of serum retinol concentrations remains steady despite the intake of vitamin A in a body.

Hypervitaminosis A Tests

Diagnosis & Tests
Bone X-rays
Blood calcium test
Cholesterol test
Liver function test
Blood test for vitamin A

Treatment of Hypervitaminosis A in Humans

  • It is generally recommended to stop taking in large amounts of vitamin A which is probably thought to be the standard treatment.
  • The vitamin E intake likely reduces the level of vitamin A reserves in a human body.
  • If it gets worse then you probably have to transplant liver.

Hypervitaminosis A in Animals

  • Although many arctic animals contain the highest level of vitamin A reserves they do not however suffer from hypervitaminosis A. The liver of most arctic animals contains the highest reserves of vitamin A which is 10 – 20 times greater than most other mammals.
  • Prominent among the arctic animals are polar bear, bearded seal, glaucous gull, and arctic fox. They are known to be the apex predators.
  • Their ability to store large amount of vitamin A is most likely to contribute to their living in the frigid arctic habitat.
  • In mice, the hypervitaminosis leads to hypothyroidism.
  • The walrus’ liver stores as much as 1624% of vitamin A while the moose’s liver contains 1920% of vitamin A reserves.

Treatment of Hypervitaminosis A in Animals

  • There are treatments that are pretty effective in alleviating toxicity level in animals despite the fact that they are not thought to be standard treatments. Some of them have worked in humans too.
  • In rabbits, vitamin E dosage prevents the side effects of vitamin A overdose.
  • In rats, taurine and cholestin have played a vital role in managing the toxic effects.
  • Vitamin K suppresses the cell ratios of vitamin A as well as thwarts hypoprothrombinemia in rats.

References & Further Reading

Singh M, Singh VN (May 1978). “Fatty liver in hypervitaminosis A: synthesis and release of hepatic triglycerides”. The American Journal of Physiology234 (5): E511–4. PMID 645903

Castaño G, Etchart C, Sookoian S (2006). “Vitamin A toxicity in a physical culturist patient: a case report and review of the literature”. Annals of Hepatology5 (4): 293–395. PMID 17151585

Weiser H, Probst HP, Bachmann H (September 1992). “Vitamin E prevents side effects of high doses of vitamin A in chicks”. Annals of the New York Academy of Sciences669: 396 8. Bibcode:1992NYASA.669..396W. doi:10.1111/j.1749-6632.1992.tb17134.x. PMID 1444058

Rutkowski M, Grzegorczyk K (June 2012). “Adverse effects of antioxidative vitamins”. International Journal of Occupational Medicine and Environmental Health25 (2): 105–21. doi:10.2478/S13382-012-0022-x. PMID 22528540

Castaño G, Etchart C, Sookoian S (2006). “Vitamin A toxicity in a physical culturist patient: a case report and review of the literature”. Annals of Hepatology5 (4): 293–395.