Several GLP-1 receptor agonists — including Ozempic, Wegovy, Rybelsus, and Mounjaro — carry an FDA Black Box Warning, the agency’s strongest safety alert. This warning highlights the potential risk of thyroid C-cell tumors, including Medullary Thyroid Carcinoma (MTC).
While the full long-term risk to humans is not yet known, the Black Box Warning exists due to concerning findings in animal studies and a lack of long-term human data. This page explains everything you need to know about these warnings and how they may affect GLP-1 drug users.
What Is a Black Box Warning?
A Black Box Warning (also called a boxed warning) is the highest level of safety caution issued by the FDA.
It appears in a bold black border on drug labels and indicates:
- a risk of serious or life-threatening adverse effects
- the need for careful patient selection
- the importance of monitoring for severe outcomes
For GLP-1 drugs, the warning covers the risk of thyroid C-cell tumors.
Which GLP-1 Drugs Carry a Black Box Warning?
The following drugs include an FDA boxed warning for thyroid C-cell tumors:
Semaglutide-based GLP-1 drugs:
- Ozempic
- Wegovy
- Rybelsus
Tirzepatide-based drugs:
- Mounjaro
- Zepbound
Other GLP-1 medications (class-wide concern):
- Trulicity (dulaglutide)
- Victoza (liraglutide)
- Saxenda (liraglutide)
While the exact risk to humans is still uncertain, the FDA requires this warning across the entire drug class.
Why Do GLP-1 Drugs Have a Black Box Warning?
The warning is based on:
- Rodent studies
Rodents given GLP-1 drugs developed:
-
- thyroid C-cell tumors
- medullary thyroid carcinoma
- other C-cell proliferative lesions
- Lack of long-term human studies
There is no reliable 10–20 year data to rule out similar risks in humans.
- Hormonal effects of GLP-1 drugs
GLP-1 receptors are present in thyroid tissue, which suggests a possible biological mechanism.
- Individual case reports
Though rare, some patients have developed thyroid abnormalities while on GLP-1 drugs.
What the Black Box Warning Says
The Black Box Warning states:
GLP-1 drugs may increase the risk of thyroid C-cell tumors, including Medullary Thyroid Carcinoma (MTC).
These medications should not be used in patients with a personal or family history of MTC or Multiple Endocrine Neoplasia syndrome type 2 (MEN-2).
Patients are advised to watch for symptoms of thyroid abnormalities and contact a healthcare provider immediately if they occur.
Thyroid Cancer Symptoms to Watch For
Symptoms of thyroid C-cell tumors or MTC include:
- Neck lump or swelling
- Persistent hoarseness
- Difficulty swallowing
- Throat tightness
- Trouble breathing
- Unexplained coughing
- Neck or ear pain
These symptoms should prompt immediate evaluation.
➡️ Thyroid Tumor Risk
Who Should Not Use GLP-1 Drugs?
The boxed warning specifies that GLP-1 drugs should not be used by people who:
- have a personal or family history of MTC
- have MEN-2 (Multiple Endocrine Neoplasia syndrome type 2)
- have unexplained thyroid nodules
- have elevated calcitonin levels
Doctors often require screening questions before prescribing.
Are Humans Actually at Risk for Thyroid Tumors?
The exact risk remains uncertain.
Evidence suggesting possible risk:
- rodent studies showed clear tumors
- GLP-1 receptors exist in human thyroid tissue
- GLP-1 drugs may influence calcitonin production
- isolated human case reports exist
Evidence suggesting lower risk:
- humans have fewer GLP-1 receptors in thyroid tissue
- clinical trials did not show a statistically significant increase
- most cases are anecdotal or isolated
The FDA’s position:
The risk cannot be ruled out.
Therefore, the strongest warning remains in place.
Other Serious GLP-1 Risks (Not Part of the Boxed Warning)
Although the boxed warning only covers thyroid tumors, GLP-1 drugs also carry serious risks such as:
- gastroparesis
- pancreatitis
- intestinal obstruction
- kidney failure
- gallbladder disease
- severe dehydration
What Patients Should Do
If you are taking a GLP-1 drug with a boxed warning:
Monitor for thyroid symptoms
Any neck swelling or difficulty swallowing requires medical evaluation.
Ask your doctor if you have thyroid risk factors
Especially family history of MTC or MEN-2.
Do not stop medication suddenly without medical guidance
Abrupt changes can cause blood sugar issues in diabetic patients.
Request calcitonin levels if concerned
Especially if you have symptoms.
Legal Rights: Thyroid Risks & GLP-1 Lawsuits
Patients who developed thyroid abnormalities, tumors, or other serious injuries while taking GLP-1 drugs may qualify for compensation.
You may have a case if you:
- developed a thyroid tumor
- were diagnosed with medullary thyroid carcinoma
- developed suspicious nodules
- needed surgery or biopsy
- were not properly warned
- suffered other severe GLP-1 complications
Compensation may include:
- medical costs
- surgery and treatment
- long-term cancer care
- lost income
- pain and suffering
- reduced quality of life
➡️ See if you qualify:
👉 GLP-1 Drug Lawsuits
👉 Ozempic Lawsuit
Related Information
- Long-Term GLP-1 Risks
- Severe GLP-1 Reactions
- Common GLP-1 Side Effects
- Thyroid Cancer Overview
- Ozempic Side Effects
- Mounjaro Side Effects
- Wegovy Side Effects
The FDA Black Box Warning for GLP-1 drugs signals the potential risk of thyroid C-cell tumors, including Medullary Thyroid Carcinoma. While human data is still limited, the warning reflects serious safety concerns and the need for monitoring. If you experienced thyroid complications or other severe adverse reactions after using a GLP-1 medication, you may have legal options.