Euthyrox: adverse event reports filed with FDA

3,596

reports as suspect product

0% of all reports · about 164 a year

133

reports, 12 months to June 2026

199 in the 12 months before

89.6%

marked serious by the reporter

48.4% across the class

2.4%

record death among outcomes, as reported

87 reports · not verified by FDA

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 Euthyrox reports recording the termmedian drug in l-thyroxine

1. Fatiguetiredness19.8%712
2. Headachehead pain13.4%482
3. Astheniaweakness or lack of energy10.7%385
4. Dizzinesslight-headedness or unsteadiness10.5%379
5. Insomniadifficulty sleeping10.4%373
6. Alopeciahair loss9.6%344
7. Blood thyroid stimulating hormone increased8.8%316
8. Anxietyanxiety8.1%293
9. Nauseafeeling sick8.1%293
10. Muscle spasmsmuscle cramps7.9%283
11. Palpitationsawareness of the heartbeat7.8%282
12. Myalgiamuscle pain7.5%270
13. Vertigoa spinning sensation7.3%263
14. Depressionlow mood7.3%262
15. Weight increasedweight gain7.3%262
16. Arthralgiajoint pain6.8%243
17. Malaisegeneral feeling of being unwell6.4%231
18. Diarrhoealoose or frequent stools6.1%220
19. Maternal exposure during pregnancythe mother took the medicine during pregnancy5.6%202
20. Loss of personal independence in daily activities5.5%199
21. Dyspnoeashortness of breath5.3%191
22. Disturbance in attentiondifficulty concentrating5.1%183
23. Irritabilityirritability5%181
24. Blood thyroid stimulating hormone decreased4.8%171
25. Hypertensionhigh blood pressure4.7%168
26. Weight decreasedweight loss4.6%167
27. Hyperthyroidismoveractive thyroid4.5%163
28. Hypothyroidismunderactive thyroid4.4%158
29. Tachycardiafast heart rate4.3%156
30. Sleep disordera sleep problem4%144

Top 30 of 948 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 6 drugs in the l-thyroxine 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 51,210 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

Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 10.6% of reports give the United States as the country of the event or reporter.

Reason for use recorded

The indication field is filled in by the reporter and is often blank; shares are of all 3,596 reports.

Drugs most often listed in the same reports

Other products listed in reports where Euthyrox is a suspect product, whatever their own role. Co-listing means the two were recorded together; it says nothing about either product's part in the event. Only the 2,500 most-reported names are counted here.

In context

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-thyroxine class

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.

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 Euthyrox as a suspect or interacting product; reports listing it only as a concomitant medication (8,950) 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.