Semaglutide drug interactions are concentrated in two places. Combining semaglutide with insulin or a sulfonylurea can increase the risk of low blood sugar. Semaglutide also delays gastric emptying, which can change how some oral medicines are absorbed. It has very low potential to inhibit or induce CYP liver enzymes, so the long interaction lists attached to many conventional drugs do not fit semaglutide well. The medication, formulation and monitoring plan matter more than a simple yes-or-no interaction checker.
The semaglutide drug interactions that matter most
Insulin and sulfonylureas change the glucose equation. Semaglutide stimulates insulin release when glucose is elevated. Insulin and sulfonylureas such as glipizide, glimepiride and glyburide lower glucose through their own pathways. Used together, their effects can overlap enough to cause hypoglycemia, including severe episodes. The June 2026 Wegovy prescribing information says the prescriber may need to reduce insulin or an insulin secretagogue when semaglutide is started. That adjustment belongs to the prescriber; it is not a fixed formula.
Delayed gastric emptying matters for selected oral drugs. Semaglutide can slow the movement of stomach contents into the intestine. The same 2026 label advises monitoring oral medicines and considering extra clinical or laboratory monitoring for drugs with a narrow therapeutic index. That term means the gap between too little and too much drug exposure is small.
What is largely absent is a conventional metabolic collision. The label says semaglutide has very low potential to inhibit or induce CYP enzymes or inhibit drug transporters. This is why a complete medication review is more useful than treating every co-medication as a prohibited combination. A change in glucose readings or laboratory values can still reflect the combination even when one medicine's blood concentration has not changed.
What common co-medications mean in practice
| Medication or class | What the evidence or label says | What the prescriber may consider |
|---|---|---|
| Insulin | Hypoglycemia risk increases when the effects overlap | Glucose readings, recent low-glucose episodes and whether the insulin dose needs adjustment |
| Sulfonylureas | The label gives the same hypoglycemia warning as for insulin | Whether the secretagogue dose needs adjustment and what monitoring is appropriate |
| Metformin | Human interaction studies found no clinically relevant change in exposure with injected semaglutide | The overall glucose plan, kidney function and tolerability rather than a CYP interaction |
| Warfarin | A healthy-volunteer study found no clinically relevant change in warfarin exposure or INR response | Continued INR monitoring because warfarin has a narrow therapeutic index and individual control can change |
| Levothyroxine | With oral semaglutide, total T4 exposure rose 33% in a single-dose study; peak exposure was unchanged | Thyroid laboratory monitoring, especially when the semaglutide formulation or timing changes |
| Ethinyl estradiol/levonorgestrel | Studies did not show reduced exposure to either component | The full contraceptive and gastrointestinal history, not an assumption based on another GLP-1 medicine |
| Other semaglutide or GLP-1 medicines | The Wegovy label does not recommend use with another semaglutide product or another GLP-1 receptor agonist | A planned transition rather than overlapping therapy |
Metformin deserves the plain answer because it is so commonly searched. In a controlled pharmacokinetic study, once-weekly injected semaglutide did not change metformin exposure to a clinically relevant degree. The same was true for warfarin, atorvastatin and digoxin (Hausner et al., Clinical Pharmacokinetics 2017). Those findings came from healthy volunteers under study conditions. They answer a pharmacokinetic question; they do not clear every individual combination.
Semaglutide and metformin are also studied together in type 2 diabetes care. The broader treatment context is covered in semaglutide for type 2 diabetes.
Tirzepatide is not an add-on for working around a semaglutide interaction. Because it also acts at the GLP-1 receptor, overlapping treatment raises a duplicate-therapy issue rather than a CYP issue. When a change is clinically appropriate, the provider plans the switch from semaglutide to tirzepatide instead of improvising an overlap.
Injection and tablet interactions are not identical
The strongest levothyroxine signal comes from oral semaglutide, not the weekly injection. In a 45-person crossover study, participants received a single 600 microgram levothyroxine dose alone and again with oral semaglutide at steady state. Total T4 exposure increased 33%, while peak concentration was unchanged (Hauge et al., Expert Opinion on Drug Metabolism & Toxicology 2021). The authors concluded that thyroid-parameter monitoring should be considered.
That specific result should not be silently transferred to every semaglutide formulation. The injected-semaglutide study found no clinically relevant exposure change for its tested oral drugs. Oral semaglutide also has strict administration conditions, so other tablets can affect semaglutide exposure as well as the reverse. A medication list therefore needs the exact product and route, not just the word "semaglutide."
Warfarin illustrates the other side of this distinction. The injected-semaglutide study found no clinically relevant change in warfarin exposure or INR response. Oral-semaglutide research likewise found no apparent change in warfarin exposure (Bækdal et al., Clinical Pharmacokinetics 2019). Even so, the label's call for extra monitoring of narrow-index oral medicines makes an INR plan more responsible than declaring the combination interaction-free.
Side effects can look like interactions
Nausea, vomiting, diarrhea and reduced food intake can alter glucose readings, hydration and how reliably an oral medicine stays down. Those are not CYP interactions, but they can change the clinical picture around diabetes drugs, blood-pressure medicines or medicines monitored by laboratory values. Semaglutide side effects explains the expected effects and the symptoms that warrant prompt clinical attention.
Alcohol has its own tolerability and glucose context. The focused guide to semaglutide and alcohol covers that question without turning it into a one-line interaction verdict.
Supplements belong on the medication list too. "Natural" does not reveal whether a product affects glucose, digestion, clotting or another treatment target. The provider needs the product name, ingredients and amount on the label to assess it.
What the provider needs before prescribing
A useful intake list includes every prescription, nonprescription medicine and supplement; the exact semaglutide formulation; insulin and sulfonylurea doses; recent glucose readings or low-glucose episodes; and medicines followed with lab tests, such as warfarin or levothyroxine. Recent vomiting, trouble keeping tablets down and planned changes to another glucose-lowering drug also change the review.
At Promise, a licensed provider reviews every request and not everyone qualifies. The provider decides whether monitoring, a co-medication adjustment or a different treatment plan is appropriate.
The formulation distinction still matters
Through Promise, semaglutide is dispensed as a compounded medication, which is different from an FDA-approved product: the formulation offered here is not FDA-approved. The interaction review still starts with the molecule's pharmacology, but the prescription and pharmacy label must identify the actual formulation and concentration being dispensed.
FDA review status is one input into care, and a licensed provider may still prescribe a compounded formulation—that decision is between the patient and the doctor. FDA explains that compounded drugs do not undergo its premarket review for safety, effectiveness or quality on its current GLP-1 compounding information page.