# Refilling a GLP-1 Pen: What Reddit Gets Right - facts Canonical page: https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit Type: Lab article ## TL;DR Refilling a GLP-1 research pen: a fact-check of Reddit on 3 ml glass cartridges, the U-100 scale (100 units = 1 ml), dialing units and planning refills. ## Facts Index | Fact ID | Category | Entity | Attribute | Value | Source | Evidence | |---|---|---|---|---|---|---| | glp1-peptide-pen-cartridge-reddit:title | identity | Refilling a GLP-1 Pen: What Reddit Gets Right | title | Refilling a GLP-1 Pen: What Reddit Gets Right | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:published | identity | Refilling a GLP-1 Pen: What Reddit Gets Right | published | 2026-08-15 | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:author | identity | Refilling a GLP-1 Pen: What Reddit Gets Right | author | Preppin' Peppers Editorial Team | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:topics | identity | Refilling a GLP-1 Pen: What Reddit Gets Right | topics | community, guides, research | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:summary | content | Refilling a GLP-1 Pen: What Reddit Gets Right | summary | Refilling a GLP-1 research pen: a fact-check of Reddit on 3 ml glass cartridges, the U-100 scale (100 units = 1 ml), dialing units and planning refills. | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:section-1 | content | Refilling a GLP-1 Pen: What Reddit Gets Right | section | What it is | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:section-2 | content | Refilling a GLP-1 Pen: What Reddit Gets Right | section | Why 3 mL cartridges | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:section-3 | content | Refilling a GLP-1 Pen: What Reddit Gets Right | section | Units and dialing | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:section-4 | content | Refilling a GLP-1 Pen: What Reddit Gets Right | section | Planning refills | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:section-5 | content | Refilling a GLP-1 Pen: What Reddit Gets Right | section | Related reading | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:section-7 | content | Refilling a GLP-1 Pen: What Reddit Gets Right | section | What the research community gets wrong about refilling a research pen with 3 mL cartridges | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit | | glp1-peptide-pen-cartridge-reddit:product-gansulin-metal-peptide-pen | products | Refilling a GLP-1 Pen: What Reddit Gets Right | references product | Gansulin Pen ยท Reusable Click-Dial, 3 ml (1-60 Units) | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://www.preppinpeppers.com/products/gansulin-metal-peptide-pen | | glp1-peptide-pen-cartridge-reddit:source-dailymed-nlm-nih-gov | source | Refilling a GLP-1 Pen: What Reddit Gets Right | cites | NovoLog (insulin aspart) , FDA/DailyMed label confirming 100 units/mL (U-100) and 3 mL PenFill cartridge delivery device - dailymed.nlm.nih.gov | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=3a1e73a2-3009-40d0-876c-b4cb2be56fc5 | | glp1-peptide-pen-cartridge-reddit:source-dailymed-nlm-nih-gov-2 | source | Refilling a GLP-1 Pen: What Reddit Gets Right | cites | Humalog (insulin lispro) , FDA/DailyMed label confirming 100 units/mL (U-100) and 3 mL single-patient-use cartridges - dailymed.nlm.nih.gov | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=c8ecbd7a-0e22-4fc7-a503-faa58c1b6f3f | | glp1-peptide-pen-cartridge-reddit:source-pubmed-ncbi-nlm-nih-gov | source | Refilling a GLP-1 Pen: What Reddit Gets Right | cites | Bohannon, Postgrad Med 1999: Insulin delivery using pen devices. Simple-to-use tools may help young and old alike - pubmed.ncbi.nlm.nih.gov | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://pubmed.ncbi.nlm.nih.gov/10560468/ | | glp1-peptide-pen-cartridge-reddit:source-pmc-ncbi-nlm-nih-gov | source | Refilling a GLP-1 Pen: What Reddit Gets Right | cites | Jonker et al., Int J Clin Pharmacol Ther 2021: First pre-filled pen device with highly purified human menopausal gonadotropin (HP-hMG, Menopur) in liquid is shown to be bioequivalent to powder for reconstitution - pmc.ncbi.nlm.nih.gov | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://pmc.ncbi.nlm.nih.gov/articles/PMC8594316/ | | glp1-peptide-pen-cartridge-reddit:source-pmc-ncbi-nlm-nih-gov-2 | source | Refilling a GLP-1 Pen: What Reddit Gets Right | cites | Lingen et al., Endocr Connect 2023: Advantages and disadvantages of connected insulin pens in diabetes management - pmc.ncbi.nlm.nih.gov | Lab article (https://www.preppinpeppers.com/blogs/the-lab/glp1-peptide-pen-cartridge-reddit) | https://pmc.ncbi.nlm.nih.gov/articles/PMC10563601/ | ## FAQ ### Why do reconstitution pens use 3 mL cartridges? Precision click-dial pens are engineered to accept standard 3 mL glass cartridges, so reconstitution math and refill schedules are conventionally built around that volume for precision and reproducibility. ### What does U-100 mean on a peptide research pen? U-100 means 100 units fit in every 1 mL of liquid. Units act like ruler tick marks, letting researchers dial to the same position each draw for consistent, repeatable volume delivery. ### How do I calculate how many draws a 3 mL cartridge holds? Divide total cartridge volume by units per draw (3 mL = 300 U-100 units). A peptide calculator planner can automate this and generate a full refill schedule from a single compound or blend entry. --- Built from PreppinPeppers store data and verified sources only. Same content for every visitor. Research and educational use only, not for human or veterinary use.