Yes. No label forbids the combination. The one interaction study used the tablet form of semaglutide [1]. In 45 healthy volunteers, total thyroxine exposure rose 33% when levothyroxine was taken with oral semaglutide 14 mg. For the weekly injection, the Ozempic label reports no clinically relevant effect on the absorption of oral drugs [3].
Two separate questions sit under this one. The first is absorption: whether the GLP-1 changes how much levothyroxine reaches the blood. The second is dose: whether losing weight changes how much levothyroxine a person needs. The labels answer the first. The second rests on thinner evidence. Thyroid cancer is a third question, answered in whether GLP-1 drugs cause thyroid cancer.
What each label says
Labels are read in this order: the product, then the interaction section.
- Ozempic injection. Semaglutide delays gastric emptying, which could affect oral drugs [3]. In clinical pharmacology trials, it did not affect their absorption to any clinically relevant degree. The label advises caution with oral drugs taken alongside it.
- Rybelsus and Ozempic tablets. Levothyroxine exposure rose 33%, with a 90% confidence interval of 1.25 to 1.42 [2]. For oral drugs with a narrow therapeutic index or that need clinical monitoring, the label says to consider more monitoring.
- Wegovy injection. The label repeats both findings [4]. The 1 mg injection did not affect oral drug absorption. The tablet raised levothyroxine exposure 33%. It advises monitoring oral drugs that have a narrow therapeutic index.
So the rule differs by form. The tablet carries a measured interaction. The pen carries a general caution. The tablet’s own dosing rules are covered in how oral semaglutide is taken.
The tablet study
Four of the trial’s five authors worked for the manufacturer [1]. They note that levothyroxine has dosing conditions similar to the tablet’s.
- 45 healthy subjects took one 600 mcg dose of levothyroxine alone.
- They took it again with oral semaglutide 14 mg at steady state.
- They also took it with SNAC 300 mg, the tablet’s absorption enhancer, alone.
Total T4 exposure rose 33% with oral semaglutide. The baseline-corrected peak did not change. SNAC alone did not affect total exposure. The authors concluded that thyroid monitoring should be considered when both drugs are used.
The same study tested the reverse direction. Five placebo tablets taken with oral semaglutide cut semaglutide exposure 34% [1]. The tablet label handles this with a timing rule. Take it with up to 4 ounces of water. Then wait at least 30 minutes before food, drinks or other oral drugs [2].
A 2025 review of GLP-1 drug interactions reached the same split [5]. It found most gastric-emptying interactions clinically insignificant. It named levothyroxine with oral semaglutide as one of two exceptions needing close monitoring. The other was oral contraceptives with tirzepatide, covered in tirzepatide and oral contraception.
The weight-loss route
Levothyroxine doses are set partly by body weight. A 2025 case report estimates the average adult need at 1.6 micrograms per kilogram [7]. The patient was stable on levothyroxine, started semaglutide and lost weight quickly. She developed palpitations and new hyperthyroidism. Her levothyroxine dose was reduced. A 2024 report described thyrotoxicosis from excess levothyroxine in a 62-year-old man whose weight fell quickly on tirzepatide [9].
Those are two patients. The 2025 authors say the mechanism is unknown. It may be increased absorption, or the weight loss itself. They advise monitoring for hyperthyroidism and expecting that a dose reduction may be needed.
A Medicare study looked at testing, not outcomes [6]. It matched 5,370 adults aged 65 or older with type 2 diabetes on a stable levothyroxine dose. About 83% had a TSH test within one year, on either drug class. The mean time to that test was about 130.5 days. The authors call the lack of any difference a missed opportunity for monitoring.
How this applies to each form
- Weekly pen. The label reports no clinically relevant absorption effect. Weight loss is the route to watch.
- Daily tablet. The label reports a 33% rise in exposure. Both routes apply.
- Compounded semaglutide. It is not FDA-approved and carries no label. No interaction data apply to it directly.
The pill and the pen are compared in the pill-versus-injection evidence.