What Causes High Vitamin B12 Levels & How to Manage It

Introduction

Vitamin B12 is an essential nutrient that is found naturally in a variety of food sources¹. Our body don’t “produce” B12 (except in gut flora, which humans cannot absorb), so we must obtain it from B12-rich foods, particularly animal-based products like meat, eggs, and dairy.  

While much attention is given to B12 deficiency, known for causing fatigue, neurological changes, and anaemia, less is said about elevated B12 levels, which can be just as important to recognise². While a high dietary intake of the vitamin rarely causes high vitamin B12, excess usually results from supplementation or injections. In many cases, this excess often signals underlying medical conditions such as liver disease, certain cancers, or blood disorders³.  

Often, vitamin B12 high means your body is producing or releasing excess B12 due to a medical condition, rather than from diet alone. Understanding its potential causes and knowing how to evaluate and manage elevated B12 levels is key for both clinicians and patients. In this article, we explore what high B12 levels mean, when to investigate further, and how to approach management effectively. 

What Is Vitamin B12, and What Are Its Normal Levels?

Vitamin B12, also known as cobalamin, is an essential water-soluble vitamin that plays a critical role in several bodily functions. It is essential for maintaining the central nervous system and helps produce healthy red blood cells, which are crucial for delivering oxygen throughout the body. Vitamin B12 also plays a key role in DNA synthesis, supports cell growth and repair, and contributes to energy metabolism. Limited evidence also suggests that B12 may support important brain functions such as memory, and may benefit heart health^1,2.

When it comes to measuring vitamin B12 levels in the blood, normal values typically range from 160 to 950 picograms per millilitre (pg/mL) or 118 to 701 picomoles per litre (pmol/L)³.

It’s important to note that having vitamin B12 levels too high doesn’t usually cause symptoms on its own, but it can be a marker for other medical concerns that need attention. Further, reference ranges may vary slightly between laboratories, as different testing methods and units may be used. For this reason, it’s best to consult with your doctor to interpret your specific results and understand what vitamin B12 high means for your health. 

What Does High B12 Mean

A high level of vitamin B12 in the blood is also known as elevated serum B12 or hypercobalaminemia⁴. Many people wonder what happens if vitamin B12 is high. While it’s not always harmful, in some cases, it can indicate an underlying health condition, such as liver or kidney dysfunction, that warrants attention^3,5.  

Although vitamin B12 is water-soluble and excess amounts are typically excreted in the urine, the body still stores significant quantities (primarily in the liver) with its levels continuously regulated. However, this storage is not responsible for high vitamin B12 levels and such elevations are rarely due to excessive dietary intake^4,5. Instead, very high serum levels often suggest impaired metabolism or an underlying medical condition. 

Causes of High B12 Levels

Understanding the causes of high vitamin B12 can help doctors identify potential underlying health conditions. Several factors can lead to elevated B12 levels, including: 

• Over-supplementation: The excessive intake of vitamin B12 through high-dose oral supplements or repeated intramuscular injections can raise blood levels of B12 temporarily⁶. 
• Liver Disease: Vitamin B12 stored in the liver can enter the blood in response to damage from conditions such as cirrhosis, hepatitis, or liver cancer⁷. 
• Kidney Dysfunction: While the kidneys do not directly excrete vitamin B12 efficiently, impaired renal function may lead to elevated serum B12 levels by reducing the clearance of B12-binding proteins or altering their metabolism, thereby contributing to B12 accumulation⁸. 
• Autoimmune Conditions: Certain autoimmune diseases may cause cell damage and disrupt normal vitamin B12 metabolism. This can lead to an unusual situation where plasma B12 levels are high, but the body’s cells are actually deficient in usable B12. Rare conditions like autoimmune lymphoproliferative syndrome (ALPS) have been linked to these changes, although overall evidence is limited⁹. 
• Myeloproliferative Disorders: These are a group of diseases (such as polycythaemia vera) that involve abnormal growth of blood cell precursors in the bone marrow. This may lead to abnormal blood cell production, potentially increasing B12 levels in the blood^3,10. 
• Certain Cancers: Blood cancers, such as leukaemia, may increase B12 levels in the blood^4,11. 

Who Is at Risk for High B12?

Certain groups are more likely to experience high vitamin B12 levels, including: 

• Individuals receiving high-dose B12 injections or supplements, especially over a prolonged period⁶. 
• Patients with liver diseases, such as fatty liver, hepatitis, or cirrhosis⁷. 
• People with chronic kidney disease, due to reduced kidney functions and reduced excretion⁸. 
• Individuals with bone marrow disorders^10,11. 
• People with certain cancers, particularly hematologic (blood-related) or liver malignancies¹¹. 
• Individuals who may have undiagnosed underlying conditions affecting B12 metabolism. 
• People with certain autoimmune conditions that may alter transport proteins (although this is rare as evidence is limited)⁹. 

Symptoms of High B12 Levels

In many cases, high vitamin B12 levels do not cause noticeable high vitamin B12 symptoms. However, when symptoms occur, often due to the underlying condition rather than the elevated B12 itself, they may include¹²: 

• Acne  
• Headaches 
• Anxiety  
• Irregular heartbeats 
• Trouble falling or staying asleep 
• Nausea  
• Fatigue 
• Dizziness 

Tests for High B12 Levels

If you’re experiencing unexplained discomfort, it’s important to check if you have any of the high vitamin B12 symptoms mentioned above, especially if you’re taking B12 supplements or injections. The main tests for checking B12 levels include: 

• Serum Vitamin B12 Test: Measures how much B12 is in your blood, but high levels don’t always mean there’s a problem; other tests are needed to be sure³. 
• Methylmalonic Acid (MMA) Test: Doesn’t check B12 directly, but if MMA is high, it usually means your body isn’t absorbing/using B12 properly, even if your B12 levels look normal.¹³ 
• Complete Blood Count (CBC): Measures the number of different cells in blood, like red and white blood cells. Abnormal results might suggest something else (like liver disease or certain conditions) is causing high B12¹⁴. 
• Liver and Kidney Function Tests: These tests help check if your liver or kidneys aren’t working properly, which can sometimes cause B12 to build up in the blood^15,16. 

If your vitamin B12 levels are too high on the serum vitamin B12 test, your doctor may recommend further testing. 

Please note that the other tests mentioned do not directly measure vitamin B12 levels but instead help assess factors related to B12 deficiency or excess. 

Health Risks Associated with High B12

In some cases, high vitamin B12 levels symptoms can include unusual symptoms like anxiety or a rapid heartbeat, which are more likely associated with the underlying condition, not the elevated B12 levels themselves. Some key health conditions associated with these symptoms include: 

• Liver Disease: In conditions like hepatitis, fatty liver disease, or liver cirrhosis, damaged liver cells may release excess B12 into the bloodstream, causing elevated levels^7,17. 
• Kidney Dysfunction: In chronic kidney disease (CKD) or renal failure, the body’s ability to filter and excrete B12 may be compromised, leading to accumulation in the blood⁸. 
• Autoimmune Conditions: Some autoimmune diseases, like ALPS, may influence B12 transport and metabolism, leading to elevated serum levels. However, these conditions are rare⁹. 
• Myeloproliferative Disorders: Conditions like polycythaemia vera could be associated with increased B12 binding proteins, leading to higher circulating B12 levels^3,10,11. 
• Blood Cancers: Conditions such as leukaemia can raise levels of the protein that binds B12^3,4. 

Note: High vitamin B12 levels symptoms are not always obvious, but some individuals may experience discomfort like dizziness or nausea. In these instances, elevated B12 may not be the root cause of illness but a biomarker that may signal a deeper health concern needing investigation.  

How to Lower B12 Levels

If you’re wondering, “What is the treatment for high vitamin B12?” it typically involves identifying and managing the underlying cause rather than reducing the vitamin levels directly. Here are some steps that may help manage high vitamin B12 symptoms: 

• Adjust supplement intake: If you’re taking high-dose B12 supplements or receiving injections, consult your doctor about reducing the dosage or frequency⁶. Unnecessary supplementation can cause artificially high levels. 
• Review medications: Some medications or multivitamins may contain B12⁶. Check labels and discuss alternatives with your doctor. 
• Manage underlying health conditions: Treating conditions like liver disease, kidney dysfunction, or blood disorders can help bring B12 levels back into a normal range^7,11. 
• Regularly check and monitor B12 levels: Routine blood tests can help track your B12 status over time and ensure that any changes are addressed early. 
• Avoid self-treatment: Never try to manage vitamin levels on your own without guidance, as doing so may mask or worsen serious health issues.  
• Consult a healthcare provider: Always speak with a doctor before making any changes, as high B12 levels may be linked to underlying health conditions that need proper evaluation and management. 

When to See a Doctor

Although rare, some people may experience side effects of high vitamin B12 levels such as headaches or skin reactions. You should consult a doctor if^3,11: 

• Your blood tests show elevated B12 levels without a clear cause. 
• You are receiving or have been advised high-dose B12 therapy and want to monitor your levels. 
• You’re concerned about long-term supplementation or vitamin use. 
• You are experiencing unexplained symptoms like fatigue, nausea, dizziness, or skin changes. 
• You have a history of liver, kidney, or blood-related conditions. 

A doctor can order additional tests to rule out serious conditions and help tailor treatment for high vitamin B12 levels specific to your health needs. 

Conclusion

Maintaining balanced vitamin B12 levels is essential for overall health and functions, such as supporting red blood cell production, nerve function, and energy metabolism. While vitamin B12 deficiency is common and well-understood, elevated B12 levels can occasionally occur. The side effects of high vitamin B12 can vary, but might be present. There is limited evidence that high vitamin B12 levels directly cause dizziness or fatigue. These symptoms are more likely linked to the underlying condition causing the elevated B12 levels, rather than the high B12 levels themselves¹⁷. 

High B12 is not usually dangerous on its own, but may point to issues like liver disease, kidney dysfunction, or blood cancers. Managing high B12 starts with identifying the causes of high vitamin B12, not just reducing intake. Regular health checkups, laboratory tests, and professional guidance related to the treatment for high vitamin B12 are key to maintaining a healthy balance and ensuring the early detection of any hidden conditions. 

Frequently Asked Questions (FAQs)

References

1. Ankar A, Kumar A. Vitamin B12 Deficiency [Internet]. Treasure Island (FL): StatPearls Publishing. 2025 Jan; [updated 2024 Sep 10; cited 2025 Apr 21]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441923/ 
2. National Institutes of Health, Office of Dietary Supplements. Vitamin B12: Fact Sheet for Consumers [Internet]. NIH; [updated 2023 Dec 15; cited 2025 Apr 21]. Available from: https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/ 
3. MedlinePlus. Vitamin B12 – Medical Encyclopedia [Internet]. U.S. National Library of Medicine; [updated 2024 Oct 19; cited 2025 Apr 21]. Available from: https://medlineplus.gov/ency/article/002403.htm 
4. Andrès E, Serraj K, Zhu J, Vermorken AJ. The pathophysiology of elevated vitamin B12 in clinical practice. QJM. 2013 Jun;106(6):505-15. doi: 10.1093/qjmed/hct051. Epub 2013 Feb 27. PMID: 23447660. Available from: https://pubmed.ncbi.nlm.nih.gov/23447660/
5. Urbanski G, Hamel JF, Prouveur B, Annweiler C, Ghali A, Cassereau J, Lozac’h P, Lavigne C, Lacombe V. Strength of the Association of Elevated Vitamin B12 and Solid Cancers: An Adjusted Case-Control Study. J Clin Med. 2020 Feb 9;9(2):474. doi: 10.3390/jcm9020474. PMID: 32050436; PMCID: PMC7073937. Available from: https://pubmed.ncbi.nlm.nih.gov/32050436/
6. National Institutes of Health (NIH) – Office of Dietary Supplements. Vitamin B12 – Health Professional Fact Sheet. [Internet]. NIH; [updated 2024 Mar 26; cited 2025 Apr 21]. Available from: https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/ 
7. Ermens AA, Vlasveld LT, Lindemans J. Significance of elevated cobalamin (vitamin B12) levels in blood. Clin Biochem. 2003 Nov;36(8):585-90. doi: 10.1016/j.clinbiochem.2003.08.004. PMID: 14636871. Available from: https://pubmed.ncbi.nlm.nih.gov/14636871/
8. Wu HHL, Wang AY. Vitamin B12 and chronic kidney disease. Vitam Horm. 2022;119:325-353. doi: 10.1016/bs.vh.2022.01.011. Epub 2022 Feb 25. PMID: 35337625. Available from: https://pubmed.ncbi.nlm.nih.gov/35337625/
9. Bowen RA, Dowdell KC, Dale JK, Drake SK, Fleisher TA, Hortin GL, Remaley AT, Nexo E, Rao VK. Elevated vitamin B₁₂ levels in autoimmune lymphoproliferative syndrome attributable to elevated haptocorrin in lymphocytes. Clin Biochem. 2012 Apr;45(6):490-2. doi: 10.1016/j.clinbiochem.2012.01.016. Epub 2012 Jan 28. PMID: 22306884; PMCID: PMC3307947. Available from: https://pubmed.ncbi.nlm.nih.gov/22306884/
10. Cinemre H, Serinkan Cinemre BF, Çekdemir D, Aydemir B, Tamer A, Yazar H. Diagnosis of vitamin B12 deficiency in patients with myeloproliferative disorders. J Investig Med. 2015 Apr;63(4):636-40. doi: 10.1097/JIM.0000000000000187. PMID: 25730455. Available from: https://pubmed.ncbi.nlm.nih.gov/25730455/
11. Fadul A, Abdalla E, Mohamed A, Ali B, Elamin N, Alsayed AA, Al-Mashdali AF, Singh K, Mohamed SF. Elevated Vitamin B12 Levels in Myeloproliferative Neoplasm (MPN) Patients: A Potential Diagnostic and Prognostic Marker. J Blood Med. 2024 Dec 27;15:549-556. doi: 10.2147/JBM.S474393. PMID: 39741578; PMCID: PMC11687131. Available from: https://pubmed.ncbi.nlm.nih.gov/39741578/
12. Budjak G, Gogineni V, Bowe Fisher V, Kirk E. Clinical manifestations of hypercobalaminemia: a case report. J Contemp Chiropr. 2024;7(1):106–108. Available from: https://journal.parker.edu/article/120325-clinical-manifestations-of-hypercobalamenia-a-case-report4 
13. Johannsen P, Ostergaard K, Christensen JE, Worm M, Rasmussen K. Methylmalonic acid in serum from patients with neurological symptoms consistent with cobalamin deficiency. Eur J Neurol. 1995 Sep;2(4):357-62. doi: 10.1111/j.1468-1331.1995.tb00139.x. PMID: 24283688. Available from: https://pubmed.ncbi.nlm.nih.gov/24283688/
14. Seo IH, Lee YJ. Usefulness of Complete Blood Count (CBC) to Assess Cardiovascular and Metabolic Diseases in Clinical Settings: A Comprehensive Literature Review. Biomedicines. 2022 Oct 25;10(11):2697. doi: 10.3390/biomedicines10112697. PMID: 36359216; PMCID: PMC9687310. Available from: https://pubmed.ncbi.nlm.nih.gov/36359216/
15. Lala V, Zubair M, Minter DA. Liver Function Tests [Internet]. Treasure Island (FL): StatPearls Publishing. 2025 Jan; [updated 2023 Jul 30; cited 2025 Apr 21]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482489/ 
16. Gounden V, Bhatt H, Jialal I. Renal Function Tests [Internet]. Treasure Island (FL): StatPearls Publishing. 2025 Jan; [updated 2024 Jul 27; cited 2025 Apr 21]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507821/ 
17. Romain M, Sviri S, Linton DM, Stav I, van Heerden PV. The role of Vitamin B12 in the critically ill–a review. Anaesth Intensive Care. 2016 Jul;44(4):447-52. doi: 10.1177/0310057X1604400410. PMID: 27456173. Available from: https://pubmed.ncbi.nlm.nih.gov/27456173/
18. Sourander A, Silwal S, Surcel HM, Hinkka-Yli-Salomäki S, Upadhyaya S, McKeague IW, Cheslack-Postava K, Brown AS. Maternal Serum Vitamin B12 during Pregnancy and Offspring Autism Spectrum Disorder. Nutrients. 2023 Apr 21;15(8):2009. doi: 10.3390/nu15082009. PMID: 37111227; PMCID: PMC10146734. Available from: https://pubmed.ncbi.nlm.nih.gov/37111227/
19. Li W, Zhao J, Zhu LL, Peng YF. Serum vitamin B12 levels and glycemic fluctuation in patients with type 2 diabetes mellitus. Ther Adv Endocrinol Metab. 2022 Jun 1;13:20420188221102800. doi: 10.1177/20420188221102800. PMID: 35677226; PMCID: PMC9168854. Available from: https://pubmed.ncbi.nlm.nih.gov/35677226/

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