Brand name · Liothyronine sodium
Cytomel: adverse event reports filed with FDA
1,230 reports list it as a suspect or interacting product, 2004–2026. Class: l-Triiodothyronine.
- 1,230
- reports as suspect product
- 0% of all reports · about 55 a year
- 28
- reports, 12 months to June 2026
- 15 in the 12 months before
- 25%
- marked serious by the reporter
- 31.7% across the class
- 0.4%
- record death among outcomes, as reported
- 5 reports · not verified by FDA
1,230 adverse event reports received by FDA list the brand name Cytomel (liothyronine sodium) as a suspect or interacting product, from February 2004 to June 2026. A further 4,168 reports list it only as a concomitant medication, and those are not counted in the figures on this page.
In the 12 months to June 2026, 28 reports listed it, up 87% from 15 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Over its reporting history that is about 55 reports a year and 0% of the 20,646,523 reports in the database, and 46.4% of the reports for the l-Triiodothyronine class. How many people take it is not in the data, so a count is not a rate of occurrence.
Reporters most often recorded drug ineffective (16.3%), fatigue (10.8%) and malaise (9.3%). A report can list several reactions, so shares add to more than 100%; 288 different terms appear across these reports. Drug ineffective is recorded in 16.3% of these reports, about the same share as in the median l-Triiodothyronine drug (19.3%).
25% of the reports are marked serious by the reporter (31.7% across the class); 0.4% record death among the outcomes and 6.3% record hospitalisation, as reported. 80.5% of the reports came from consumers, and the largest patient age group is 45 to 64 (21.5%). FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event."
Reports by month, five years
Reports by the month FDA received them. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.
By year received
2026 covers reports received through June 2026 only.
Reactions recorded in the reports
share of Cytomel reports recording the termmedian drug in l-triiodothyronine
- Drug ineffectivethe medicine did not work as expected16.3%201
- Fatiguetiredness10.8%133
- Malaisegeneral feeling of being unwell9.3%114
- Feeling abnormalfeeling odd or not right8.5%105
- Weight increasedweight gain8.1%100
- Alopeciahair loss7.6%93
- Palpitationsawareness of the heartbeat6.6%81
- Headachehead pain5.3%65
- Astheniaweakness or lack of energy4.9%60
- Off label useused for a purpose or in a way not on the label4.1%51
- Insomniadifficulty sleeping4%49
- Hypothyroidismunderactive thyroid3.6%44
- Dyspnoeashortness of breath3.4%42
- Painpain, site not specified3%37
- Dizzinesslight-headedness or unsteadiness2.9%36
- Hypersensitivityan allergic-type reaction2.8%35
- Nauseafeeling sick2.8%34
- Rashskin rash2.8%34
- Heart rate increaseda fast heart rate reading2.5%31
- Coeliac disease2.3%28
- Pruritusitching2.3%28
- Hyperthyroidismoveractive thyroid2.2%27
- Weight decreasedweight loss2.2%27
- Diarrhoealoose or frequent stools2.1%26
- Anxietyanxiety2%25
- Arthralgiajoint pain2%25
- Product quality issuea problem with the product itself2%25
- Urticariahives2%25
- Condition aggravatedthe condition being treated got worse2%24
Top 30 of 288 MedDRA preferred terms recorded across these reports, with a plain-language gloss where one is available. One report can record several terms. The hollow bar is the median share across the 2 drugs in the l-triiodothyronine class; it describes the reports, not the patients. 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."
Outcomes recorded
Outcome flags as the reporter set them; a report can carry several, and "other serious" is FDA's own category for serious reports outside the named outcomes. Grey bar: all 2,653 reports in the class. FDA has not verified any outcome and states that the reports "cannot be used to estimate the incidence of these events."
Patients and reporters
Patient age
Patient sex
Who reported
Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 96% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Hypothyroidism | 290 | 23.6% |
| Thyroid disorder | 103 | 8.4% |
| Autoimmune thyroiditis | 56 | 4.6% |
| Tri-iodothyronine decreased | 14 | 1.1% |
| Thyroidectomy | 8 | 0.7% |
| Thyroid hormone replacement therapy | 3 | 0.2% |
The indication field is filled in by the reporter and is often blank; shares are of all 1,230 reports.
In context
| Measure | Cytomel | l-Triiodothyronine | All reports |
|---|---|---|---|
| Reports as suspect product | 1,230 | 2,653 | 20,646,523 |
| Share of that pool | — | 46.4% | 0% |
| Reports, latest 12 months | 28 | — | 1,332,454 |
| Marked serious | 25% | 31.7% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 4 | 5 | 91 |
| Hospitalisation recorded, per 1,000 reports | 63 | 144 | 213 |
| Consumer-filed share | 80.5% | 77.9% | 45.8% |
| Top term, share of reports | Drug ineffective 16.3% | median 19.3% | 6.3% |
Shares are of reports, not of patients treated. The number of people taking a product is not in the data, so none of these figures is a rate, and differences between columns reflect who takes a product, who reports and how long it has been sold. 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."
Other drugs in the l-triiodothyronine class
| Drug | Name type | Reports | Latest 12 months | Marked serious |
|---|---|---|---|---|
| Liothyronine sodium | generic | 1,423 | 68 | 37.6% |
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." A brand and its generic are separate rows because reporters name them separately.
Questions about Cytomel reports
How many adverse event reports has FDA received for Cytomel?
1,230 reports list Cytomel as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 28 of them arrived in the latest 12 months. Another 4,168 list it only as a concomitant medication.
What reactions are recorded in Cytomel reports?
drug ineffective (16.3%), fatigue (10.8%), malaise (9.3%), feeling abnormal (8.5%) and weight increased (8.1%). These are MedDRA preferred terms coded from what the reporter described; a report can list several, and a term's presence is not a finding that Cytomel was responsible.
How serious are the reports?
25% are marked serious by the reporter. Among the outcomes recorded, 0.4% of reports include death and 6.3% include hospitalisation. FDA has not verified these outcomes and states that the reports "cannot be used to estimate the incidence" of the events.
Who files these reports?
consumer or non-health professional (80.5%), physician (6.5%) and other health professional (5.9%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Cytomel rising?
28 reports in the 12 months to June 2026, up 87% from 15 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Counts also move with how many people take a product, its time on the market and publicity.
Do these reports show that Cytomel was responsible for these reactions?
No. FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event." The reaction may relate to the condition being treated, to other medicines, or to something else.
Is this a list of the side effects of Cytomel?
No. It is a count of what was reported to FDA. The adverse reactions observed in clinical studies are printed on the FDA-approved label, which a pharmacist or clinician can go through with you.
How do I report an adverse event?
Consumers and health professionals can report to FDA through MedWatch (Form FDA 3500 online, or 1-800-FDA-1088), or to the manufacturer, which must pass reports on. 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 report counts here when it lists Cytomel as a suspect or interacting product; reports listing it only as a concomitant medication (4,168) are excluded. 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.