phentermine Side Effects
Also known as: Adipex-P, Lomaira
Analysis of 6,109 adverse event reports submitted to the FDA from 2004 to 2025.
Total Reports
6,109
Death-Related
390
6.4% of reports
Hospitalizations
1,481
24.2% 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 390 reports where death was an outcome. These are voluntarily reported and do not establish causation.
| Reaction | Reports |
|---|---|
| COMPLETED SUICIDE | 95 |
| DRUG ABUSE | 91 |
| TOXICITY TO VARIOUS AGENTS | 77 |
| DEATH | 60 |
| CARDIO-RESPIRATORY ARREST | 43 |
| CARDIAC ARREST | 42 |
| RESPIRATORY ARREST | 33 |
| OVERDOSE | 17 |
| POISONING | 15 |
| ACUTE KIDNEY INJURY | 12 |
| SUSPECTED SUICIDE | 12 |
| HYPOTENSION | 10 |
| INTENTIONAL DRUG MISUSE | 9 |
| METABOLIC ACIDOSIS | 9 |
| COMA | 8 |
| DEPRESSED LEVEL OF CONSCIOUSNESS | 7 |
| DRUG TOXICITY | 7 |
| HYPOGLYCAEMIA | 7 |
| PULMONARY EMBOLISM | 7 |
| RHABDOMYOLYSIS | 7 |
Reactions in Hospitalization Reports
Top reactions in 1,481 reports where hospitalization was an outcome.
| Reaction | Reports |
|---|---|
| PAIN | 186 |
| NAUSEA | 154 |
| ANXIETY | 134 |
| PULMONARY EMBOLISM | 127 |
| INJURY | 110 |
| VOMITING | 100 |
| DEEP VEIN THROMBOSIS | 98 |
| ABDOMINAL PAIN | 90 |
| DYSPNOEA | 86 |
| CHOLECYSTITIS CHRONIC | 83 |
| HEADACHE | 81 |
| ACUTE KIDNEY INJURY | 79 |
| OFF LABEL USE | 76 |
| FATIGUE | 75 |
| EMOTIONAL DISTRESS | 74 |
| CHEST PAIN | 72 |
| DEPRESSION | 70 |
| CHOLELITHIASIS | 67 |
| DIARRHOEA | 65 |
| DRUG INTERACTION | 65 |
Nearby — Related Medications
What the FAERS Data Reveals About phentermine Side Effects
The FDA Adverse Event Reporting System (FAERS) contains 6,109 voluntary reports linked to phentermine and its brand equivalents (Adipex-P, Lomaira), spanning 2004 through 2025. Of those, 390 (6.4%) listed death as an outcome and 1,481 (24.2%) 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, 85% were female and 14% male; age distribution skews toward 18-44, with 1,819 reports in that bracket. The single most reported reaction is drug ineffective with 537 submissions, followed by nausea and pain.
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.