📅 Last Updated: September 4, 2026 | All sources verified at time of publication
This page lists the primary clinical, regulatory, and scientific sources referenced throughout LevelsRX Review. We prioritize peer-reviewed clinical trials, FDA documents, and official prescribing information. Where we reference third-party comparisons, we note the source explicitly.
Semaglutide Clinical Trials
STEP 1 Trial: Once-Weekly Semaglutide in Adults with Overweight or Obesity
Wilding JPH, et al. N Engl J Med. 2021;384(11):989-1002.
DOI: 10.1056/NEJMoa2032183
Used for: semaglutide average weight loss (~15% body weight), STEP-1 trial results, 68-week duration data.
STEP 2 Trial: Semaglutide for the Treatment of Obesity (Type 2 Diabetes Subgroup)
Davies M, et al. Lancet. 2021;397(10278):971-984.
DOI: 10.1016/S0140-6736(21)00213-0
Used for: semaglutide efficacy in patients with type 2 diabetes, metabolic improvements.
STEP 3 Trial: Semaglutide and Intensive Behavioral Therapy
Wadden TA, et al. JAMA. 2021;325(14):1403-1413.
DOI: 10.1001/jama.2021.1831
Used for: context on lifestyle intervention + GLP-1 combination outcomes.
Tirzepatide Clinical Trials
SURMOUNT-1 Trial: Tirzepatide Once Weekly for the Treatment of Obesity
Jastreboff AM, et al. N Engl J Med. 2022;387(3):205-216.
DOI: 10.1056/NEJMoa2206038
Used for: tirzepatide 22.5% weight loss figure (highest dose, 72 weeks), SURMOUNT-1 trial results, % achieving ≥5%, ≥15%, ≥20% weight loss.
SURMOUNT-2 Trial: Tirzepatide in Adults with Obesity and Type 2 Diabetes
Garvey WT, et al. Lancet. 2023;402(10402):613-626.
DOI: 10.1016/S0140-6736(23)01200-X
Used for: tirzepatide efficacy in metabolic comorbidity context.
Semaglutide vs. Tirzepatide Comparisons
Comparative Effectiveness of Semaglutide vs Tirzepatide in Real-World Settings
Jastreboff AM, et al. JAMA Intern Med. 2023;183(9):967-975.
DOI: 10.1001/jamainternmed.2023.2871
Used for: real-world head-to-head comparison claims; tirzepatide producing greater weight reduction across BMI categories.
GLP-1 Mechanism and Pharmacology
GLP-1 Receptor Agonists for Weight Management
Müller TD, et al. Nat Metab. 2022;4(8):965-977.
Used for: GLP-1 mechanism explanations, appetite suppression, gastric emptying, food noise context.
Tirzepatide: A Dual GIP and GLP-1 Receptor Agonist
Farzam K, et al. StatPearls. Treasure Island (FL): StatPearls Publishing; 2024.
Used for: tirzepatide dual mechanism explanation, GIP receptor agonism context.
Compounding Pharmacy Regulatory Framework
FDA: Compounding and the FDA — Questions and Answers
U.S. Food and Drug Administration. Current as of 2024.
https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers
Used for: compounding pharmacy regulatory framework, FDA authorization during drug shortages, distinction from brand-name drugs.
FDA Drug Shortage Database — Semaglutide and Tirzepatide Status
U.S. Food and Drug Administration Drug Shortages. Updated periodically.
https://www.accessdata.fda.gov/scripts/drugshortages/
Used for: current drug shortage status context for compounding authorization.
Muscle Preservation and Protein Intake on GLP-1
Preservation of Lean Mass During GLP-1 Therapy: Role of Protein Intake and Resistance Training
Bikou O, et al. Nutrients. 2023;15(4):1006.
Used for: protein intake recommendations on GLP-1, lean mass preservation context, resistance training benefit claims.
Protein Recommendations for GLP-1 Users: Clinical Guidance
Based on consensus guidance from American Society for Metabolic and Bariatric Surgery (ASMBS) protein intake recommendations for weight loss patients.
Used for: 0.7–1.0g protein per lb lean body mass recommendation context.
Disclaimer
This reference list is provided for transparency and to allow readers to verify clinical claims made across this site. It is not exhaustive of all research on these topics. Clinical science evolves, and individual studies may be superseded by newer evidence. Consult a licensed healthcare provider for current clinical guidance.