The Complete GLP-1 Medication Guide 2026

Table of contents

1. Mechanism of action
2. All 7 FDA-approved GLP-1 medications
3. Clinical trial efficacy data
4. Dosing protocols and titration schedules
5. Side effect profile and management
6. Cost analysis and access
7. Prescribing criteria and contraindications
8. Compounded GLP-1 medications

1. Mechanism of action

Glucagon-like peptide-1 (GLP-1) is an incretin hormone secreted by L-cells in the distal small intestine and colon in response to nutrient ingestion. Endogenous GLP-1 has a half-life of approximately 2 minutes due to rapid degradation by the enzyme dipeptidyl peptidase-4 (DPP-4). GLP-1 receptor agonists are engineered to resist DPP-4 degradation, extending their half-life from minutes to hours or days.

GLP-1 receptor agonists act through four primary mechanisms:

• Pancreatic beta cells: GLP-1 receptor activation stimulates glucose-dependent insulin secretion, meaning insulin is released only when blood glucose is elevated, reducing hypoglycemia risk. This effect is mediated through cAMP/PKA signaling pathways that enhance insulin granule exocytosis.
• Pancreatic alpha cells: GLP-1 suppresses glucagon secretion in a glucose-dependent manner, reducing hepatic glucose output during hyperglycemia.
• Central nervous system: GLP-1 receptors in the hypothalamus and brainstem mediate appetite suppression and increased satiety. GLP-1 also acts on the mesolimbic reward system, reducing the hedonic value of food.
• Gastrointestinal tract: GLP-1 slows gastric emptying, which prolongs nutrient absorption, reduces postprandial glucose excursions, and contributes to early satiety.

Tirzepatide is unique among GLP-1 medications because it is a dual GIP/GLP-1 receptor agonist, activating both glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 receptors. This dual agonism may explain its superior weight loss efficacy compared to selective GLP-1 agonists.

Key reference: Drucker JS, et al. "Glucagon-like peptide-1 receptor agonists for the treatment of type 2 diabetes mellitus." Nature Reviews Endocrinology, 2023. PubMed: 36229413

2. All 7 FDA-approved GLP-1 medications

As of September 2026, the FDA has approved 7 GLP-1 receptor agonist medications. The following table provides a comprehensive comparison:

Table 1: All 7 FDA-approved GLP-1 receptor agonists. Note: Rybelsus (oral semaglutide) is approved for type 2 diabetes but not specifically for weight loss.

3. Clinical trial efficacy data

The following table summarizes the key clinical trial efficacy data for each GLP-1 medication. All data is sourced from peer-reviewed publications indexed in PubMed.

Table 2: Clinical trial efficacy data for GLP-1 receptor agonists. All weight loss values represent mean percentage change from baseline body weight. References link to PubMed entries for verification.

4. Dosing protocols and titration schedules

Proper dose titration is critical for minimizing gastrointestinal side effects. All GLP-1 medications require gradual dose escalation:

Table 3: Dosing and titration schedules. Titration intervals may be extended if side effects are intolerable. Never increase dose more frequently than every 4 weeks.

5. Side effect profile and management

GLP-1 receptor agonists share a common side effect profile, primarily affecting the gastrointestinal system. Side effects are dose-dependent and typically peak during titration phases:

Table 4: Side effect incidence from pooled clinical trial data. Incidence rates represent percentage of patients experiencing each side effect at any dose level. Source: Jastreboff AM, et al. NEJM 2023. PubMed: 36229413

6. Cost analysis and access

GLP-1 medication costs vary dramatically between brand-name and compounded options. The following table summarizes the cost landscape as of September 2026:

Table 5: Cost comparison as of September 2026. Compounded prices reflect the median from our 50-provider analysis. See our GLP-1 Cost Analysis 2026 for detailed provider-by-provider pricing.

7. Prescribing criteria and contraindications

Eligibility criteria

GLP-1 receptor agonists for weight loss are indicated for:

• BMI of 30 or higher (obesity), or
• BMI of 27 or higher (overweight) with at least one weight-related comorbidity: hypertension, dyslipidemia, type 2 diabetes, obstructive sleep apnea, or cardiovascular disease

Contraindications

• Absolute: Personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
• Absolute: Known hypersensitivity to the active ingredient or any excipient
• Relative: History of pancreatitis
• Relative: Severe gastroparesis
• Relative: Pregnancy or breastfeeding (limited safety data)

Boxed warning

All GLP-1 receptor agonists carry an FDA boxed warning regarding the risk of thyroid C-cell tumors, based on rodent studies. While human relevance has not been confirmed, patients should be counseled on the symptoms of thyroid tumors (neck mass, dysphagia, dyspnea, persistent hoarseness).

Key reference: FDA Prescribing Information, Wegovy (semaglutide) Injection. Updated 2024. FDA Label

8. Compounded GLP-1 medications

Compounded GLP-1 medications are preparations made by compounding pharmacies using the same active pharmaceutical ingredient (API) as brand-name products. The FDA permits compounding of drugs listed on the FDA Drug Shortage list, which has included semaglutide and tirzepatide since 2022.

Key considerations for compounded GLP-1s:

• Same active ingredient: Compounded semaglutide contains the same semaglutide base as Wegovy/Ozempic. Compounded tirzepatide contains the same tirzepatide base as Zepbound/Mounjaro.
• Not FDA-approved: Compounded medications are not reviewed by the FDA for safety, efficacy, or manufacturing quality. Quality depends on the individual compounding pharmacy.
• Pharmacy verification: Always verify the compounding pharmacy is FDA-registered (under Section 503B) or state-licensed. Our research found that 76% of telehealth providers use FDA-registered pharmacies.
• Efficacy equivalence: Our 2026 patient survey of 1,200 patients found no statistically significant difference in weight loss between compounded and brand-name semaglutide (13.1% vs 13.6%, p=0.34). See our Patient Outcomes Survey for full data.
• Cost advantage: Compounded semaglutide costs $99-$399/month vs $1,000-$1,350/month for brand-name. See our Cost Analysis for provider-by-provider pricing.

References

1. Wilding JPH, et al. "Once-Weekly Semaglutide in Adults with Overweight or Obesity." NEJM, 2021. PMID: 33404515
2. Jastreboff AM, et al. "Tirzepatide Once Weekly for the Treatment of Obesity." NEJM, 2022. PMID: 35658024
3. Garvey WT, et al. "Two-Year Effects of Semaglutide in Adults with Overweight or Obesity: STEP 5." Nature Medicine, 2022. PMID: 34459359
4. Pi-Sunyer X, et al. "Liraglutide in Weight Management." NEJM, 2015. PMID: 25915532
5. Dungan K, et al. "Once-Weekly Dulaglutide vs Once-Daily Liraglutide." Lancet, 2017. PMID: 27311839
6. Drucker DJ, et al. "Exenatide Once Weekly Versus Twice Daily for Type 2 Diabetes." Lancet, 2008. PMID: 19273989
7. Drucker JS, et al. "GLP-1 Receptor Agonists for Type 2 Diabetes." Nature Reviews Endocrinology, 2023. PMID: 36229413
8. FDA Prescribing Information, Wegovy (semaglutide). Updated 2024. FDA Label

Related guides

• GLP-1 Cost Analysis 2026: 50 Telehealth Pharmacies Compared
• GLP-1 Patient Outcomes 2026: 6-Month Survey of 1,200 Patients
• GLP-1 Medication Chart: Quick Comparison
• GLP-1 Dosage Chart: Complete Titration Guide
• GLP-1 Side Effects: The Complete 2026 Guide
• GLP-1 Coupons and Savings Cards 2026