Pharmacologic class (EPC) · 2 drug pages

Vitamin B12: adverse event reports filed with FDA

26,500 reports list a drug in this class as a suspect or interacting product, 2004–2026.

Read first · FDA's statement on these data

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product. openFDA, FDA

FDA adds: "There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event." The information in these reports "cannot be used to estimate the incidence of these events."

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

26,500
reports across the class: 0.1% of all reports; 2,471
reports, 12 months to June 2026: 3,556 in the 12 months before; 95.6%
marked serious by the reporter: 57.4% across all reports; 2
drugs with a page: brand and generic names counted separately

Vitamin B12 is a pharmacologic class (an FDA Established Pharmacologic Class) with 2 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 26,500 adverse event reports received by FDA, 0.1% of the database, from January 2004 to June 2026.

2,471 reports arrived in the 12 months to June 2026, down 31% from 3,556 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 95.6% of the class's reports are marked serious, 22.8% record death among the outcomes and 39.6% record hospitalisation, as reported.

Across the class the reactions recorded most often are pain (35.5%), drug ineffective (34.2%) and systemic lupus erythematosus (33.4%). The class median share shown beside each term is the middle value across the member drugs; it is the comparison used on every drug page in this class.

The members table is ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Drugs in the class

Drug	Name type	Reports	Latest 12 months	Marked serious	Top term recorded
Folic acid	generic	24,051	2,285	96.5%	Pain
Cyanocobalamin	generic	2,449	186	87.8%	Gastrooesophageal reflux disease

Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Reports by month, five years

FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

Reactions recorded across the class

share of class reports recording the termmedian drug in the class

Painpain, site not specified35.5%9,410
Drug ineffectivethe medicine did not work as expected34.2%9,071
Systemic lupus erythematosuslupus, an autoimmune disease33.4%8,857
Alopeciahair loss32.8%8,681
Rheumatoid arthritisrheumatoid arthritis, an inflammatory joint disease32.6%8,643
Pemphigus32.3%8,565
Abdominal discomfortstomach discomfort32%8,487
Fatiguetiredness32%8,479
Glossodynia29.6%7,844
Swellingswelling26.5%7,028
Hand deformity25.8%6,850
Rashskin rash24.8%6,579
Arthropathy24.3%6,452
Wound23.9%6,331
Contraindicated product administered23.5%6,238
Maternal exposure during pregnancythe mother took the medicine during pregnancy23.5%6,236
Joint swellinga swollen joint22.6%5,992
Drug intolerancethe medicine was not tolerated22.2%5,874
Synovitis22%5,835
Infusion related reactiona reaction during or soon after an infusion21.6%5,715
Pericarditisinflammation of the sac around the heart21.1%5,583
Arthralgiajoint pain20.8%5,517
Off label useused for a purpose or in a way not on the label20.4%5,410
Hepatic enzyme increasedraised liver enzymes20.3%5,370
Hypersensitivityan allergic-type reaction20.2%5,360

Solid bar: share of all class reports. Hollow bar: the median share across the 2 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death22.8%6,034

Life-threatening21.6%5,734

Hospitalisation (initial or prolonged)39.6%10,501

Disability27.2%7,200

Congenital anomaly12.5%3,308

Other serious81.7%21,643

Not serious4.4%1,153

Patient age

Under 20.9%226

2 to 110.3%90

12 to 170.5%122

18 to 4427.1%7,193

45 to 6416.4%4,357

65 to 748.1%2,136

75 and over6%1,591

Age not given40.7%10,785

Who reported

Physician19%5,033

Pharmacist3.2%858

Other health professional61.1%16,185

Lawyer0%9

Consumer or non-health professional15.4%4,082

Not given1.3%333

Grey bar: all 20,646,523 reports in the database. Outcome flags are as the reporter set them and are not verified by FDA.

Questions about Vitamin B12 reports

Which drugs are in the Vitamin B12 class on this site?

Folic acid and Cyanocobalamin. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

26,500 reports through June 2026, 2,471 of them in the latest 12 months. A report listing two drugs of the class counts once for each.

What reactions are recorded most often?

pain (35.5%), drug ineffective (34.2%), systemic lupus erythematosus (33.4%), alopecia (32.8%) and rheumatoid arthritis (32.6%).

Can the members table be used to rank the drugs?

No. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." Drugs differ in how many people take them, in the conditions they treat, in time on the market and in how diligently reports are collected.

How do I report an adverse event?

Through FDA MedWatch (Form FDA 3500, or 1-800-FDA-1088) or to the manufacturer. See the guide on how to report.

Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A class is the Established Pharmacologic Class most often attached to a drug's reports by openFDA's label harmonisation, or from the NDC Directory where reports carry none. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.

Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.