GLP-1 Receptor Agonists: How to Select the Right Agent Within the Class

Start with the label indication

The class splits into two groups. Wegovy injection and Wegovy tablets, Saxenda and FDA-approved generic liraglutide for weight, Zepbound and Foundayo are approved for weight management [1][2][3][4]. Ozempic, Rybelsus, Victoza, Trulicity, Byetta, Mounjaro, Soliqua and Xultophy are type 2 diabetes products, and Trulicity and Mounjaro carry no weight-loss indication [6][7][8][9][3].

Some diabetes labels add cardiovascular or kidney claims. Ozempic is labeled to reduce CV risk in type 2 diabetes with established CV disease and for kidney outcomes in type 2 diabetes with chronic kidney disease; Victoza for CV risk reduction in type 2 diabetes with established CV disease; Trulicity for CV risk reduction in type 2 diabetes with established CV disease or multiple CV risk factors [6][7][8]. Wegovy injection and tablets are labeled to reduce major adverse CV events in adults with established CV disease who have obesity or overweight, and Wegovy injection also carries a noncirrhotic MASH indication with moderate to advanced fibrosis [1].

Tirzepatide is labeled a GIP and GLP-1 receptor agonist, a dual agonist rather than a pure GLP-1 agonist, though it is usually grouped with this class [3].

What the weight trials showed

In SURMOUNT-1, 2,539 adults with obesity or overweight and no diabetes took tirzepatide 5, 10 or 15 mg or placebo for 72 weeks: weight change was 15.0%, 19.5% and 20.9% with the three doses versus 3.1% with placebo [11]. In STEP 1, 1,961 adults took semaglutide 2.4 mg weekly or placebo for 68 weeks: 14.9% versus 2.4% [12].

SURMOUNT-5 was an open-label, 72-week head-to-head trial of 751 adults with obesity and no diabetes: maximum tolerated tirzepatide produced 20.2% weight loss versus 13.7% with maximum tolerated semaglutide, and waist circumference fell 18.4 cm versus 13.0 cm [5]. The trials do not establish whether the added GIP activity accounts for that difference [3][5].

Foundayo's label reports two 72-week trials. In Trial 1 (3,127 adults with obesity or overweight, no diabetes) weight change was 7.4%, 8.3% and 11.1% at 5.5, 9 and 17.2 mg versus 2.1% with placebo; in Trial 2 (1,613 adults with type 2 diabetes and BMI 27 or higher) it was 5.1%, 7.0% and 9.6% versus 2.5% [4]. Saxenda's label study enrolled 3,731 adults for 56 weeks: 7.4% weight loss versus 3.0% with placebo, and at least 5% weight loss in 62.3% versus 34.4% [2].

Rates from different trials and populations are not directly comparable [1].

What the diabetes head-to-head trials showed

SURPASS-2 was an open-label, 40-week trial in 1,879 adults with type 2 diabetes: HbA1c fell 2.01, 2.24 and 2.30 points with tirzepatide 5, 10 and 15 mg versus 1.86 points with semaglutide 1 mg, and weight fell 1.9, 3.6 and 5.5 kg more than with semaglutide [13].

SUSTAIN 7 was an open-label, 40-week trial in 1,201 adults with type 2 diabetes: semaglutide 0.5 and 1 mg lowered HbA1c 1.5 and 1.8 points versus 1.1 and 1.4 with dulaglutide 0.75 and 1.5 mg, and weight fell 4.6 and 6.5 kg versus 2.3 and 3.0 kg [14].

Dosing: weekly, daily, twice daily or a tablet

Weekly injections are Ozempic, Wegovy injection, Trulicity, Mounjaro and Zepbound; once-daily injections are Victoza, Saxenda and generic liraglutide; Byetta is injected twice daily; once-daily tablets are Rybelsus, Ozempic tablets, Wegovy tablets and Foundayo [1][10][4].

The three semaglutide tablets are taken on an empty stomach with up to 4 ounces of water, 30 minutes before food or other oral drugs, while Foundayo is taken once daily with or without food [1][10][4]. Foundayo starts at 0.8 mg and rises no faster than every 30 days (2.5, 5.5, 9, 14.5, 17.2 mg), to a maximum of 17.2 mg [4]. Every product in the class starts low and steps up over weeks to reduce gastrointestinal side effects [1][4]. Semaglutide's half-life is about one week [1]; orforglipron's is about 29 to 49 hours [4].

The evidence behind the cardiovascular and kidney claims

SELECT followed 17,604 adults with established CV disease and a BMI of 27 or higher without diabetes for a mean of 39.8 months: CV death, heart attack or stroke occurred in 6.5% on semaglutide 2.4 mg versus 8.0% on placebo (hazard ratio 0.80) [15]. SUSTAIN-6 followed 3,297 adults with type 2 diabetes for 104 weeks: 6.6% versus 8.9% (hazard ratio 0.74) [16].

Tolerability: the numbers the labels report

Wegovy 2.4 mg over 68 weeks: nausea 44% versus 16%, vomiting 24% versus 6%, diarrhea 30% versus 16%, constipation 24% versus 11% [1]. Foundayo 17.2 mg over 72 weeks: 35%, 24%, 25% and 24% versus 10%, 4%, 11% and 9% [4]. Zepbound 15 mg pooled over up to 72 weeks: 28%, 13%, 23% and 11% versus 8%, 2%, 8% and 5% [3].

Permanent discontinuation for adverse reactions was 6.8% versus 3.2% with Wegovy, 8% versus 3% with Foundayo (10% at 17.2 mg), and 6.7% versus 3.4% with Zepbound 15 mg [1][4][3]. Hair loss was reported by 3% versus 1% on Wegovy, 5% versus 2% on Foundayo 17.2 mg (7% of women versus 0.9% of men), and 4% to 5% versus 1% on Zepbound [1][4][3].

Interactions that differ by agent

Birth control advice is product-specific. Tirzepatide labels advise a non-oral method or an added barrier method for 4 weeks after starting and after each dose increase, and Foundayo for 30 days after starting and after each increase [3][4]. Semaglutide labels carry no such advice, and a tablet interaction study found no clinically significant change in ethinyl estradiol or levonorgestrel [1].

Every GLP-1 drug raises hypoglycemia risk with insulin or a sulfonylurea, and the labels advise considering a lower dose of the insulin or sulfonylurea at the start [4][1]. In Foundayo's type 2 diabetes trial, glucose below 54 mg/dL occurred in 7% of people taking a sulfonylurea versus 0.5% of those not [4].

Wegovy's label says to consider increased monitoring for oral medicines with a narrow therapeutic index; Foundayo's label warns that delayed gastric emptying may affect absorption of oral medicines [1][4]. The Foundayo label advises avoiding strong CYP3A4 inducers, limits Foundayo to 9 mg daily with a strong CYP3A4 inhibitor, and limits concomitant simvastatin to 20 mg daily [4]. Oral semaglutide raised levothyroxine exposure 33% [1].

Safety warnings shared across the class

Semaglutide, liraglutide, dulaglutide, tirzepatide and Xultophy products carry boxed warnings for rodent thyroid C-cell tumors, with human relevance unknown, and are contraindicated in people with a personal or family history of medullary thyroid carcinoma or MEN 2 [1][7][17][8][3]. Foundayo's boxed warning uses different wording: orforglipron is not pharmacologically active in rats or mice and caused no rodent tumors, while the same MTC and MEN 2 contraindication applies [4]. Byetta and Soliqua carry no boxed warning [9][18].

Labels also warn about acute pancreatitis (discontinue if suspected); severe GI reactions with no recommendation for use in severe gastroparesis; acute kidney injury from dehydration; gallbladder disease; serious hypersensitivity; diabetic retinopathy complications in type 2 diabetes; and pulmonary aspiration during general anesthesia or deep sedation [1][4]. Mean resting heart rate rose 1 to 4 bpm with Wegovy, 4 to 5 bpm with Foundayo versus 0.5 bpm on placebo, and 1 to 3 bpm with tirzepatide [1][4][3]. Weight loss offers no benefit in pregnancy, and the Wegovy, Foundayo and Zepbound labels advise stopping when pregnancy is recognized; the Wegovy label adds at least 2 months before a planned pregnancy [1][4][3].

What is not an FDA-approved option

Compounded semaglutide and tirzepatide are not FDA approved and are not reviewed for safety, effectiveness or quality; as of 2026-05-31 FDA had received 990 adverse event reports for compounded semaglutide and more than 730 for compounded tirzepatide [19][20]. No retatrutide or cagrilintide product is FDA approved, and FDA states both cannot be used in compounding and have not been found safe and effective for any condition [20].