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READING SHELF / FIVE SOURCES

# Where our facts come from.

These peptide references support the distinctions in this guide. They cover approved product information, medicines made to order and concerns about research-only sales from the U.S. Food and Drug Administration (FDA). They are background reading, not a personal care plan.

TODAY / U.S. ONLY

[Start a Promise Peptides visit for metabolic support](https://mypromise.com/solutions/metabolic-support-fat-loss?utm_source=nextgen&utm_medium=affiliate&utm_campaign=reference&utm_content=hero)

Promise Peptides prescribes now. A licensed provider reviews each request and decides whether to prescribe. Not everyone qualifies. Compounded medicines are made to order, not FDA-approved.

NextGen may earn money when readers become Promise patients.

TARGET STUDY / 02

GIP + GLP-1

GIP and GLP-1 are hormone signals. A receptor is a cell’s signal receiver. Tirzepatide acts on two receptor types.

01

## Five sources, with a clear job for each.

FDA is short for the U.S. Food and Drug Administration. GLP-1 and GIP are names for hormone signals. The product information below describes specific approved medicines; it does not give FDA approval to a compounded version.

01 /

[FDA: what compounding means](https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers)

Explains medicines made to order and how they differ from FDA-approved products.

02 /

[FDA: risks of compounded medicines](https://www.fda.gov/drugs/human-drug-compounding/understanding-risks-compounded-drugs)

Explains that compounded medicines do not receive FDA approval before they are sold.

03 /

[FDA: concerns about unapproved GLP-1 drugs](https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss)

Covers unapproved products, including retatrutide, sold with research-only labels.

04 /

[Semaglutide: approved product information](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ee06186f-2aa3-4990-a760-757579d8f77b)

Records the GLP-1 target and the status of a specific approved semaglutide product.

05 /

[Tirzepatide: approved product information](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=487cd7e7-434c-4925-99fa-aa80b1cc776b)

Records the GIP and GLP-1 targets and the status of a specific approved tirzepatide product.

02

## How to read the distinctions.

Compounding means making a medicine to order. Compounded medicines are not FDA-approved. The FDA sources explain that difference and the risks that come with products it has not reviewed before sale.

Retatrutide is investigational: still being studied in clinical trials. It is not FDA-approved and is not available by prescription. The research-sales source addresses unapproved retatrutide offered outside those trial conditions.

We do not use study results to predict an individual's outcome. A source about an approved product also cannot establish the contents or quality of a research-only product sold online.

## Reading informs the question. Review informs care.

Promise prescribes semaglutide and tirzepatide now through licensed U.S. providers. A provider reviews every request and decides whether to prescribe. Not everyone qualifies.

TODAY / U.S. ONLY

[Start a Promise Peptides visit for metabolic support](https://mypromise.com/solutions/metabolic-support-fat-loss?utm_source=nextgen&utm_medium=affiliate&utm_campaign=reference&utm_content=closing)

Promise Peptides prescribes now. A licensed provider reviews each request and decides whether to prescribe. Not everyone qualifies. Compounded medicines are made to order, not FDA-approved.

NextGen may earn money when readers become Promise patients.

[Retatrutide](/retatrutide/)

[Tirzepatide](/tirzepatide/)

[Semaglutide](/semaglutide/)

[About](/about/)

[References](/references/)

[Contact](/contact/)

[Promise Peptides: weight visit](https://mypromise.com/products?utm_source=nextgen&utm_medium=affiliate&utm_campaign=reference&utm_content=footer)

NextGen may earn money when readers become Promise patients.

NextGen is not affiliated with any company that has used the name NextGen Peptides or Next Gen Peptides.

NextGen puts peptide questions into plain words; it is a guide, not a clinic, pharmacy or seller.

Facts reviewed 8 October 2026

[Read as Markdown](/references/index.md)