cyanocobalamin Side Effects
Also known as: Vitamin B12
Analysis of 31,083 adverse event reports submitted to the FDA from 2004 to 2025.
Total Reports
31,083
Death-Related
3,041
9.8% of reports
Hospitalizations
12,543
40.4% of reports
Top Indication
Product Used For Unknown Indication
Most Reported Adverse Reactions
Who Reports Side Effects
Gender Distribution
Age Distribution
Reporting Trend by Year
Reactions in Death Reports
Top reactions reported in 3,041 reports where death was an outcome. These are voluntarily reported and do not establish causation.
| Reaction | Reports |
|---|---|
| DEATH | 1,103 |
| FATIGUE | 349 |
| OFF LABEL USE | 346 |
| ASTHENIA | 289 |
| VOMITING | 269 |
| CONDITION AGGRAVATED | 261 |
| GENERAL PHYSICAL HEALTH DETERIORATION | 259 |
| DIARRHOEA | 258 |
| CONFUSIONAL STATE | 256 |
| HYPERTENSION | 253 |
| HYPOAESTHESIA | 250 |
| RHEUMATOID ARTHRITIS | 250 |
| DRUG INEFFECTIVE | 244 |
| HELICOBACTER INFECTION | 241 |
| ARTHRALGIA | 240 |
| SYSTEMIC LUPUS ERYTHEMATOSUS | 240 |
| TYPE 2 DIABETES MELLITUS | 240 |
| PAIN | 237 |
| INFUSION RELATED REACTION | 235 |
| JOINT SWELLING | 235 |
Reactions in Hospitalization Reports
Top reactions in 12,543 reports where hospitalization was an outcome.
| Reaction | Reports |
|---|---|
| FATIGUE | 1,311 |
| NAUSEA | 1,256 |
| DYSPNOEA | 1,139 |
| PNEUMONIA | 1,078 |
| VOMITING | 1,065 |
| HEADACHE | 1,064 |
| FALL | 1,026 |
| ASTHENIA | 1,015 |
| PAIN | 979 |
| DIARRHOEA | 973 |
| PYREXIA | 967 |
| OFF LABEL USE | 945 |
| HYPERTENSION | 903 |
| DRUG INEFFECTIVE | 822 |
| ARTHRALGIA | 781 |
| ABDOMINAL PAIN | 735 |
| MALAISE | 731 |
| CONDITION AGGRAVATED | 714 |
| GASTROOESOPHAGEAL REFLUX DISEASE | 705 |
| DIZZINESS | 700 |
Nearby — Related Medications
What the FAERS Data Reveals About cyanocobalamin Side Effects
The FDA Adverse Event Reporting System (FAERS) contains 31,083 voluntary reports linked to cyanocobalamin and its brand equivalents (Vitamin B12), spanning 2004 through 2025. Of those, 3,041 (9.8%) listed death as an outcome and 12,543 (40.4%) involved hospitalization. The most common indication reported alongside adverse events was Product Used For Unknown Indication.
Demographic breakdowns help contextualize who is being exposed to the drug. Of reports with known sex, 65% were female and 35% male; age distribution skews toward 45-64, with 6,929 reports in that bracket. The single most reported reaction is fatigue with 3,101 submissions, followed by nausea and off label use.
FAERS is a signal-detection tool, not a scorecard. Reports are voluntary, and a single case may list multiple suspect drugs, so numbers above should not be read as incidence rates or per-patient risk. Widely prescribed drugs naturally accumulate more reports than niche therapies even when individual risk is low. These aggregates are useful for spotting patterns that merit further pharmacovigilance, not for choosing between medications. This page is for educational reference only and is not medical advice — speak with a licensed clinician about any side-effect concerns.
Read our methodology — how this data is sourced, computed, and verified.