# Hypervitaminosis
**Hypervitaminosis** is the condition of toxicity caused by excessive intake or accumulation of one or more vitamins, and it arises almost exclusively from the fat-soluble vitamins A and D, which the body stores in the liver and in fat rather than excreting promptly.[1](https://www.jpsionline.com/articles/overdose-risk-of-vitamins-a-review.pdf) Water-soluble vitamins are generally excreted in urine when taken in excess, so sustained overdose states are rare for them. In practice the term covers two distinct clinical pictures: hypervitaminosis A, with neurological, skeletal, hepatic, and skin effects, and hypervitaminosis D, whose central manifestation is hypercalcemia (abnormally high blood calcium).[2](https://www.sciencedirect.com/science/article/abs/pii/S0009898126002998) • [3](https://pmc.ncbi.nlm.nih.gov/articles/PMC6158375/) Toxicity from ordinary food alone is uncommon; most cases follow high-dose supplements, retinoid medications, or dosing errors.[4](https://www.ncbi.nlm.nih.gov/books/NBK532916/)
| Key fact | Detail |
|---|---|
| Principal vitamins involved | Fat-soluble vitamins A and D, which are stored by the body for longer periods than water-soluble vitamins[1](https://www.jpsionline.com/articles/overdose-risk-of-vitamins-a-review.pdf) |
| Acute vitamin A toxicity | Occurs within days to weeks after one or a few very high doses, typically more than 100 times the RDA; symptoms include severe headache, blurred vision, nausea, dizziness, aching muscles, and coordination problems[5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/) |
| Adult upper limit, preformed vitamin A | 3,000 mcg RAE per day from food and supplements combined (600 mcg for children under 4 years)[5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/) |
| Chronic vitamin A toxicity | Long-term ingestion above about 25,000 IU/day in adults, with dermatological, skeletal, neurological, and hepatic manifestations[6](https://www.sciencedirect.com/science/article/pii/S0009898126002998) |
| Vitamin D toxicity hallmark | Serum 25-hydroxyvitamin D above 150 ng/ml (375 nmol/l), with hypercalcemia symptoms such as confusion, vomiting, polyuria, and dehydration[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC6158375/) |
| Leading cause | Non-prescription supplement misuse, identified in 67.7% of cases in a systematic review of 31 studies[2](https://www.sciencedirect.com/science/article/abs/pii/S0009898126002998) |
| Carotenoid exception | No tolerable upper limit has been set for beta-carotene or other provitamin A carotenoids, because regulated intestinal conversion rarely causes toxicity[5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/) • [4](https://www.ncbi.nlm.nih.gov/books/NBK532916/) |
## Vitamin A toxicity
[Vitamin A](https://www.edgepedia.org/vitamin-a) is a group of fat-soluble retinoids, primarily retinol and retinyl esters, stored mostly in the liver. Because the body stores excess amounts, levels can accumulate over time.[5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/) Toxicity is divided into acute and chronic forms. Acute hypervitaminosis A follows one or a few very large doses, typically more than 100 times the Recommended Dietary Allowance, and produces severe headache, blurred vision, nausea, dizziness, aching muscles, and coordination problems within days to weeks; in severe cases cerebrospinal fluid pressure rises, leading to drowsiness, coma, and even death.[5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/) Chronic hypervitaminosis A, from regular consumption of high doses, causes dry skin, painful muscles and joints, fatigue, depression, and abnormal liver test results.[5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/) A 2026 systematic review of 31 studies found hypercalcemia the most frequent adverse effect (29.0% of cases), followed by gastrointestinal, neurological, hepatobiliary, musculoskeletal, and dermatological manifestations; acute cases presented more often with neurological signs such as headache, diplopia, and raised intracranial pressure, while chronic cases more often involved hepatobiliary and skeletal complications.[2](https://www.sciencedirect.com/science/article/abs/pii/S0009898126002998)
**Dose thresholds and limits.** The Food and Nutrition Board of the National Academies has set tolerable upper intake levels (ULs) for preformed vitamin A that apply to food and supplement intakes combined, based on liver abnormalities, teratogenic effects, and toxicity in infants and children. The UL is 600 mcg RAE/day from birth through age 3, 900 mcg from ages 4 to 8, 1,700 mcg from ages 9 to 13, 2,800 mcg from ages 14 to 18, and 3,000 mcg from age 19 onward, including pregnancy and lactation.[5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/) Chronic toxicity in adults is described with long-term ingestion above 25,000 IU/day, against a normal adult requirement of roughly 700 to 900 mcg RAE (about 2,300 to 4,300 IU) per day.[6](https://www.sciencedirect.com/science/article/pii/S0009898126002998) These ULs apply only to retinol and its ester forms, such as retinyl palmitate; when a supplement derives part of its vitamin A from beta-carotene, only the preformed fraction counts against the limit.[5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/)
**Carotenoids are a separate case.** The body converts provitamin A carotenoids such as beta-carotene to retinol in the intestine through a regulated enzyme, so dietary carotenoids rarely cause toxicity, and no UL has been established for them.[4](https://www.ncbi.nlm.nih.gov/books/NBK532916/) • [5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/) The Food and Nutrition Board nevertheless advises against beta-carotene supplements for the general population: the ATBC trial found that 20 mg/day of beta-carotene for 5 to 8 years increased lung cancer risk by 18% and overall mortality by 8% in male smokers, and the CARET trial in smokers and asbestos-exposed workers was stopped early after supplements increased lung cancer risk by 28%.[5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/)
**Teratogenicity and retinoid drugs.** Total intakes of preformed vitamin A above the UL, as well as systemic retinoid medications such as isotretinoin (used for severe acne) and etretinate (used for severe psoriasis), can cause congenital birth defects.[5](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/) [Retinoid](https://www.edgepedia.org/retinoid) drugs are chemically distinct from natural vitamin A but act through the same retinoid receptors, so retinoid toxicity is often clinically indistinguishable from hypervitaminosis A and is considered part of the same clinical spectrum.[4](https://www.ncbi.nlm.nih.gov/books/NBK532916/)
## Vitamin D toxicity
[Hypervitaminosis D](https://www.edgepedia.org/vitamin-d-toxicity), or vitamin D toxicity, produces severe hypercalcemia through excessive long-term intake of vitamin D, malfunction of the vitamin D metabolic pathway, or coincident disease that produces active vitamin D metabolite locally.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC6158375/) The most often noted symptoms are confusion, apathy, recurrent vomiting, abdominal pain, polyuria, polydipsia, and dehydration; serum 25-hydroxyvitamin D concentrations above 150 ng/ml (375 nmol/l) are the hallmark of toxicity from overdosing.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC6158375/) Exogenous toxicity usually follows inadvertent or improper intake of very high doses of pharmacological preparations; endogenous forms arise from excessive production of 1,25-dihydroxyvitamin D in granulomatous disorders and some lymphomas, or reduced degradation of that metabolite in idiopathic infantile hypercalcemia.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC6158375/) Treatment consists of stopping vitamin D, restricting dietary calcium, restoring intravascular volume, and, in severe cases, giving corticosteroids or bisphosphonates.[7](https://www.merckmanuals.com/professional/nutritional-disorders/vitamin-deficiency%2C-dependency%2C-and-toxicity/vitamin-d-toxicity?media=print)
**How much is too much.** A meta-analysis of 22 randomized trials with 12,952 participants found that daily vitamin D doses of 3,200 to 4,000 IU, near the adult tolerable upper intake level of 4,000 IU, increased the risk of hypercalcemia (relative risk 2.21, about 4 excess cases per 1,000 individuals) as well as falls and hospitalization, though risks of kidney stones and mortality did not differ significantly.[8](https://pubmed.ncbi.nlm.nih.gov/36853379/) Case reports also document malpractice-related intoxication, including a series of 62 patients given multiple injections of 600,000 IU each who presented with hypercalcemia and acute kidney injury, and pediatric hypercalcemia linked to a fish oil supplement whose stated dose was roughly 4,000 times lower than the actual dose.[9](https://pmc.ncbi.nlm.nih.gov/articles/PMC7427646) • [10](https://pmc.ncbi.nlm.nih.gov/articles/PMC5980613/)
## Causes and at-risk groups
**Supplements dominate.** Although diet by itself rarely causes toxicity, regularly eating foods high in preformed vitamin A, liver, fish liver oils, eggs, and dairy products, can bring it about.[4](https://www.ncbi.nlm.nih.gov/books/NBK532916/) In the systematic review of hypervitaminosis A cases, vitamin A capsules or tablets accounted for 67.7% of identified sources, and the authors characterized the condition as predominantly arising from non-prescription supplement misuse.[2](https://www.sciencedirect.com/science/article/abs/pii/S0009898126002998) Additional risk factors for vitamin A toxicity include underlying liver disease, hyperlipidemia, high alcohol intake, conditions affecting vitamin A metabolism, and older age.[4](https://www.ncbi.nlm.nih.gov/books/NBK532916/) In regions where vitamin A deficiency is prevalent, large-scale supplementation and food fortification programs can raise toxicity risk if dosing guidelines are not strictly followed.[4](https://www.ncbi.nlm.nih.gov/books/NBK532916/) By contrast, multivitamin and mineral products providing nutrients at no more than 100% of the recommended dietary allowance have shown only minor adverse effects in randomized trials and do not by themselves produce excess intake.[11](https://pubmed.ncbi.nlm.nih.gov/27553772/)
## History
[Vitamin A toxicity](https://www.edgepedia.org/hypervitaminosis-a) was first described in arctic explorers and Alaskan Natives who became ill after eating large quantities of polar bear and seal liver, which contain extremely high concentrations of preformed vitamin A; specimens from [Greenland](https://www.edgepedia.org/greenland) expeditions tested at 12,000 to 26,000 IU per gram.[4](https://www.ncbi.nlm.nih.gov/books/NBK532916/) • [12](https://www.ncbi.nlm.nih.gov/books/NBK548165/pdf/Bookshelf_NBK548165.pdf) The clinical entity was more clearly defined in the early 1950s, when diagnosis rested on a history of excessive ingestion, increased blood vitamin A levels, and cortical hyperostoses.[13](https://www.nejm.org/doi/10.1056/NEJM195201172460303) In the 1940s, infant vitamin A toxicity from dietary overdosage was recognized as painful periostitis, rarely progressing to premature closure of lower limb epiphyses; a 2007 historical review linked these human cases to "hyena disease" in calves, in which vitamin A-enriched grain caused physeal obliteration and shortened hind limbs with a hyena-like gait.[14](https://pubmed.ncbi.nlm.nih.gov/17909784/) Bone anomalies in ancient human fossils have also been attributed to hypervitaminosis A.[15](https://dergipark.org.tr/en/download/article-file/864941)
## Diagnosis and management
Clinical recognition can be difficult because symptoms such as fatigue, headache, dry skin, bone pain, nausea, laboratory abnormalities, and increased intracranial pressure overlap with other disorders; a thorough dietary, supplement, and medication history is central to diagnosis.[4](https://www.ncbi.nlm.nih.gov/books/NBK532916/) For hypervitaminosis A, the review evidence identifies prompt discontinuation of vitamin A intake as the cornerstone of management, supported by symptomatic therapies including bisphosphonates, prednisone, intravenous fluids, calcitonin, orthopedic surgery, and, in severe hepatic cases, liver transplantation; measurement of retinyl esters rather than total retinol is recommended for accurate diagnosis.[2](https://www.sciencedirect.com/science/article/abs/pii/S0009898126002998) For vitamin D toxicity, management proceeds through stabilization and supportive therapy, stopping vitamin D, restricting dietary calcium, and adding corticosteroids or bisphosphonates when toxicity is severe.[7](https://www.merckmanuals.com/professional/nutritional-disorders/vitamin-deficiency%2C-dependency%2C-and-toxicity/vitamin-d-toxicity?media=print) • [9](https://pmc.ncbi.nlm.nih.gov/articles/PMC7427646)
## References
1. [Overdose Risk of Vitamins: A Review, Dhyani et al., J. Pharm. Sci. Innov. 2019](https://www.jpsionline.com/articles/overdose-risk-of-vitamins-a-review.pdf)
2. [Clinical Spectrum and Management of Hypervitaminosis A: A Systematic Review of Case-Based Evidence, Padmakar, Clinical Chemistry and Laboratory Medicine (2026)](https://www.sciencedirect.com/science/article/abs/pii/S0009898126002998)
3. [Vitamin D Toxicity: A Clinical Perspective, Marcinkowska & Brown, Frontiers in Endocrinology (2018)](https://pmc.ncbi.nlm.nih.gov/articles/PMC6158375/)
4. [Vitamin A Toxicity, StatPearls, NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK532916/)
5. [Vitamin A and Carotenoids, Fact Sheet for Health Professionals, NIH Office of Dietary Supplements](https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/)
6. [clinical spectrum and management of hypervitaminosis a:a systematic review of case-based evidence - sciencedirect](https://www.sciencedirect.com/science/article/pii/S0009898126002998)
7. [Vitamin D Toxicity, Merck Manual Professional Edition](https://www.merckmanuals.com/professional/nutritional-disorders/vitamin-deficiency%2C-dependency%2C-and-toxicity/vitamin-d-toxicity?media=print)
8. [Long-term supplementation with 3200 to 4000 IU of vitamin D daily and adverse events: a systematic review and meta-analysis of randomized controlled trials (2023)](https://pubmed.ncbi.nlm.nih.gov/36853379/)
9. [Vitamin D Toxicity, Lim et al., BMJ (2020)](https://pmc.ncbi.nlm.nih.gov/articles/PMC7427646)
10. [A review of the growing risk of vitamin D toxicity from inappropriate practice, Taylor & Davies (2018)](https://pmc.ncbi.nlm.nih.gov/articles/PMC5980613/)
11. [Multivitamin/mineral supplements: Rationale and safety, a systematic review (2016)](https://pubmed.ncbi.nlm.nih.gov/27553772/)
12. [Vitamin A, StatPearls / NCBI Bookshelf (polar bear and seal liver vitamin A levels)](https://www.ncbi.nlm.nih.gov/books/NBK548165/pdf/Bookshelf_NBK548165.pdf)
13. [Hypervitaminosis A: A Case Report, New England Journal of Medicine, Vol. 246, No. 3 (1952)](https://www.nejm.org/doi/10.1056/NEJM195201172460303)
14. [Hypervitaminosis A-induced premature closure of epiphyses in humans and calves (hyena disease): a historical review, Pediatric Radiology (2007)](https://pubmed.ncbi.nlm.nih.gov/17909784/)
15. [Review Article on vitamin A toxicity history, DergiPark](https://dergipark.org.tr/en/download/article-file/864941)
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*Topic: Encyclopedia › Life and health › Human health and medicine › Diseases and injuries › Digestive, metabolic, and endocrine conditions › Malnutrition and nutritional disorders*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 21, 2026 · Edited: Sep 30, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license