Is Orotic Acid the Same as Vitamin B13?

December 19, 2025 •

3 min read

Historically, the term "Vitamin B13" was used for orotic acid, an intermediary molecule involved in the body's synthesis of pyrimidines, which are essential for creating nucleic acids. Today, however, orotic acid is no longer considered a true vitamin by the scientific community because the human body produces it endogenously and does not require it from the diet.

Quick Summary

This article clarifies the relationship between orotic acid and the obsolete term 'Vitamin B13,' explaining why orotic acid is not a vitamin but an essential biological compound synthesized by the human body. It details the history of its classification and describes its metabolic functions, dietary sources, and modern supplemental uses, including its role as a mineral carrier.

Key Points

Misclassification: Orotic acid was once incorrectly named Vitamin B13, but modern science does not recognize it as a vitamin.
Endogenous Production: The human body naturally produces orotic acid, eliminating the need for dietary intake, a key characteristic of a true vitamin.
Metabolic Role: Orotic acid is a crucial intermediate in the synthesis of pyrimidines, which are building blocks for DNA and RNA.
Mineral Carrier: In supplements, orotic acid is often used as a carrier molecule to enhance the absorption of minerals like magnesium and potassium.
Orotic Aciduria: Genetic defects related to orotic acid metabolism can cause hereditary orotic aciduria, a rare condition that leads to serious health issues.
Supplement Caution: Any product marketed as 'Vitamin B13' is using an obsolete term and may not be necessary for general health if not addressing a specific metabolic issue.

The Historical Identification of Orotic Acid

For a period in the mid-20th century, orotic acid was classified as Vitamin B13. Scientists in the 1940s initially isolated orotic acid from distillers' dried solubles and believed it to be an essential nutrient. However, further research revealed that mammals can synthesize orotic acid themselves through the pyrimidine biosynthesis pathway. Because a true vitamin is an organic compound required by an organism that cannot be synthesized in sufficient quantities by that organism, orotic acid fails this key criterion.

The Shift in Scientific Consensus

The reclassification of orotic acid from a vitamin to a pseudo-vitamin or non-essential nutrient was a significant moment in nutritional science. The term "Vitamin B13" is now widely considered a misnomer, and it is not recognized as a vitamin by major scientific bodies, including the International Union of Pure and Applied Chemistry (IUPAC) or the World Health Organization (WHO). The list of official B vitamins includes B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), and B12 (cobalamin).

The Role of Orotic Acid in Human Metabolism

Despite not being a vitamin, orotic acid is a critical metabolic intermediate. It is a precursor to uridine monophosphate (UMP), which is vital for the synthesis of pyrimidine nucleotides. These nucleotides are fundamental components of DNA and RNA, as well as several cofactors necessary for cellular function.

Key Metabolic Functions:

Nucleic Acid Synthesis: Orotic acid is a building block for pyrimidines, which are used to construct DNA and RNA.
Cellular Regeneration: Its role in nucleic acid synthesis makes it essential for cell growth and repair processes.
Mineral Transport: Orotic acid can chelate, or bind, with minerals like magnesium, potassium, and lithium, forming highly bioavailable compounds. Magnesium orotate, for example, is used in some supplements due to its potential cardiovascular benefits.
Myocardial Energy: Studies have shown that orotic acid may improve the energy status and function of heart tissue, especially after an infarction.

Sources and Health Implications

Orotic acid is naturally present in some foods, primarily milk and dairy products like whey and buttermilk. However, since the human body can produce it, there is no dietary requirement for it. In rare cases of inherited metabolic disorders, a deficiency in the enzymes that process orotic acid can lead to a buildup, causing a condition known as hereditary orotic aciduria.

Symptoms of orotic aciduria can include:

Megaloblastic anemia
Developmental delays
Failure to thrive in infants
Orotic acid crystals in the urine (crystalluria)

Treatment for hereditary orotic aciduria often involves uridine supplementation, which helps normalize the metabolic pathway.

Comparison: Orotic Acid vs. True B Vitamins


Feature	Orotic Acid (formerly 'Vitamin B13')	True B Vitamins (e.g., B1, B12)
Essentiality	Non-essential; produced by the human body.	Essential; must be obtained from the diet.
Body Production	Synthesized endogenously as a metabolic intermediate.	Cannot be produced by the body in sufficient amounts.
Function	Involved in pyrimidine synthesis, mineral transport, and cellular regeneration.	Coenzymes involved in a vast array of metabolic processes, like energy production and cell growth.
Deficiency Cause	Primarily genetic defects leading to metabolic disorders like orotic aciduria.	Insufficient dietary intake, malabsorption, or certain medical conditions.
Supplemental Use	Used as a mineral carrier (e.g., magnesium orotate) and as a metabolic support agent.	Corrects dietary deficiency; supports various metabolic and neurological functions.
Official Status	Unrecognized as a vitamin; the term 'Vitamin B13' is obsolete.	Officially recognized by the scientific community.

Conclusion: A Distinction Based on Science

In summary, while historical texts and some supplement marketers may reference "Vitamin B13," it is not the same as orotic acid in a modern scientific context. Orotic acid is a naturally occurring compound and vital metabolic intermediate that the body can create itself, rendering its classification as a vitamin incorrect. The confusion stems from a historical misidentification that has since been corrected based on a more complete understanding of metabolism. Today, orotic acid's primary uses are in targeted metabolic support and as a carrier molecule for mineral supplements, a far cry from the function of a true, essential vitamin. Consumers should be aware of this distinction to make informed decisions about nutrition and supplementation. For more information on established nutritional guidelines, the National Institutes of Health provides extensive resources on essential vitamins.

Frequently Asked Questions

Orotic acid is no longer considered a vitamin because the human body can produce it internally. A true vitamin is an essential nutrient that the body cannot synthesize on its own and must be obtained through the diet.

The primary function of orotic acid is its role as an intermediate metabolite in the synthesis of pyrimidine nucleotides. These are essential components of nucleic acids, such as DNA and RNA, which are crucial for cellular processes.

Today, orotic acid is used in dietary supplements primarily as a carrier molecule to increase the bioavailability of minerals like magnesium and potassium. Magnesium orotate, for example, is promoted for cardiovascular health.

Yes, orotic acid is found in small amounts in dairy products, such as milk, whey, and buttermilk. However, since the body produces its own, dietary intake is not necessary for general health.

Hereditary orotic aciduria is a rare genetic disorder where the body is unable to metabolize orotic acid properly, causing it to build up in the body. This can lead to issues like megaloblastic anemia and developmental delays.

No, Vitamin B13 is not the same as Vitamin B12. Vitamin B12 is a separate, officially recognized vitamin (cobalamin), whereas the term 'Vitamin B13' for orotic acid is obsolete and scientifically inaccurate.

While orotic acid in supplements is not a vitamin, the compounds are generally safe. However, consumers should be aware that the 'Vitamin B13' label is misleading and consult a healthcare provider before starting any new supplement regimen.