Who should NOT take semaglutide
Absolute contraindications and cautions
Quick read · 7 min
Do not take semaglutide if you have a personal or family history of medullary thyroid cancer (MTC), Multiple Endocrine Neoplasia type 2 (MEN 2), or are pregnant. Use caution if you have diabetic eye disease, a history of pancreatitis, or severe kidney disease. Tell your doctor about all of these before starting.
- •Absolute "do not take": MTC history, MEN 2, pregnancy, severe pancreatitis history
- •Use with caution: Diabetic retinopathy, gallbladder disease, severe kidney disease, severe GI problems
- •Oral contraceptive pills may be less effective — use backup contraception
- •Insulin & sulfonylureas: increased low blood sugar risk — your doses need adjustment
- •Tell your doctor: thyroid history, allergies, other medications, eating disorders
Based on clinical trials · No rankings · Every claim linked to source
Semaglutide and tirzepatide can cause thyroid C-cell tumours in rodents. This has not been observed in humans, but the FDA requires this warning.
Who is at risk: People with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia type 2 (MEN 2). If this is you, do not take this medication.
Do NOT take if you have:
These are absolute contraindications. Talk to your doctor before starting if any apply to you.
MTC is a rare thyroid cancer. Semaglutide carries an FDA black box warning for thyroid C-cell tumours (shown in animals, not confirmed in humans). If you have personal history, do not take this drug. If multiple close relatives had MTC, get genetic testing for MEN 2 first.
MEN 2 is a genetic syndrome that increases thyroid cancer risk. If you have MEN 2, semaglutide is contraindicated. Ask your doctor about genetic testing if you have a strong family history of thyroid cancer.
Semaglutide causes birth defects in animal studies (skeletal problems, developmental delays). Stop at least 2 months before trying to conceive. If you become pregnant while taking it, stop immediately and contact your doctor.
If you have had acute pancreatitis (sudden inflammation of the pancreas), semaglutide carries a risk of triggering it again. Talk to your doctor — the risk-benefit may not favour this drug.
If you have had anaphylaxis, swelling of the throat, or severe rash from any GLP-1 drug, do not take semaglutide. Tell your doctor immediately.
Pregnancy and breastfeeding
Talk to your doctor about weight loss options if you are planning pregnancy or breastfeeding. Other approaches may be safer.
Talk to your doctor if you have:
These are not automatic contraindications, but require a conversation with your doctor before starting.
Semaglutide can worsen existing diabetic retinopathy, especially if blood sugar drops quickly. Most relevant if you have type 2 diabetes with existing eye damage. Your doctor will monitor your eyes. This is not an absolute contraindication — just needs careful monitoring.
Rapid weight loss increases gallstone formation risk. If you have a history of gallstones, your doctor may monitor with ultrasounds. Not an absolute contraindication, but requires discussion.
Semaglutide slows stomach emptying, which could worsen severe GI conditions. Mild GI issues (like IBS) are usually fine. Talk to your doctor about your specific condition.
Limited data on semaglutide in severe kidney disease. Your doctor may recommend caution or dose adjustment. Mild to moderate kidney disease is usually okay with monitoring.
A baseline thyroid ultrasound may be recommended before starting. Thyroid monitoring during treatment is reasonable. Not an absolute contraindication, but requires discussion.
Quick eligibility summary
Likely a good fit if:
- •BMI 30+ (or 27+ with obesity-related conditions)
- •No personal or family history of MTC / MEN 2
- •Not pregnant or planning pregnancy within 2 months
- •Willing to inject once weekly or take pill daily
- •No severe kidney, liver, or pancreatic disease
Talk to your doctor if:
- •You have a family history of thyroid cancer
- •You have diabetic eye disease or retinopathy
- •You have a history of gallstones
- •You take insulin or diabetes medications
- •You take blood thinners like warfarin
Not for you if:
- •Personal or family history of MTC
- •Known MEN 2 syndrome
- •Currently pregnant or planning pregnancy soon
- •Severe pancreas or kidney disease
- •Severe allergy to any GLP-1 drug
Next step most people take
Based on clinical trials · No rankings · Every claim linked to source
Last reviewed: March 2026