What the label lists and what reports show
Phentermine side effects
Phentermine's FDA label lists its adverse reactions in its own words. FAERS holds 6,389 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is nausea (517 reports).
- Generic listed
- DEA Schedule IV
Check it at the source: the phentermine FDA label on DailyMed (effective April 18, 2024, KVK-Tech, Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe following adverse reactions are described, or described in greater detail, in other sections: Primary pulmonary hypertension [ see Warnings and Precautions ( 5.2 ) ] Valvular heart disease [ see Warnings and Precautions ( 5.3 ) ] Effect on the ability to engage in potentially hazardous tasks [ see Warnings and Precautions ( 5.5 ) ] Withdrawal effects following prolonged high dosage administration [ see Drug Abuse and Dependence ( 9.3 ) ] The following adverse reactions to phentermine have been identified: Cardiovascular: Primary pulmonary hypertension and/or regurgitant cardiac valvular disease, palpitation, tachycardia, elevation of blood pressure, ischemic events. Central Nervous System: Overstimulation, restlessness, dizziness, insomnia, euphoria, dysphoria, tremor, headache, psychosis. …
Source: FDA drug label, KVK-Tech, Inc., effective April 18, 2024 (SPL set b963f7bb-fa65-4e28-81c9-282fbe70a6a6), via openFDA; the full label on DailyMed
What do FAERS reports show?
6,389 reports list phentermine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 415 are coded as a death and 1,557 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 22 reactions below, 5 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Phentermine: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions