# Peptide Pen Compatibility: Which Peptides Work | RefillPen

URL: https://www.refillpen.com/peptide-pen-compatibility

Last updated: 2026-10-19T14:15:43.659Z

> A reusable peptide pen for standard 3 mL cartridges: works with retatrutide, semaglutide, tirzepatide, Glow, GHK-Cu, BPC-157 and 67 label names.

## Which peptides work with a reusable peptide pen?

### Can I use a RefillPen with tirzepatide or semaglutide?

Yes. RefillPen is a reusable pen for standard 3 mL cartridges you fill yourself. It measures in units and isn’t built for any single compound, and we make pen labels for tirzepatide (Tirz) and semaglutide (Sema). RefillPen is not a prefilled pen and isn’t affiliated with any drug brand.

### Can I use a RefillPen for retatrutide?

Yes. Load retatrutide in a standard 3 mL cartridge, prime, and dial in units like any other peptide. We make Reta labels, including a limited-edition Pink Lemonade color.

### Can I use a RefillPen for BPC-157, TB-500, GHK-Cu or NAD+?

Yes. The pen works the same way whatever the cartridge holds: fill a standard 3 mL cartridge, load it, prime, and dial in units. We make labels for all four, and for 63 other names listed above.

### Can I put Glow, Klow or Wolverine blends in a RefillPen?

Yes. A blend goes in one cartridge just like a single peptide, and we make Glow, Klow and Wolverine labels so the pen says which blend is inside.

### Does RefillPen sell peptides or prefilled pens?

No. RefillPen sells the pens, 3 mL cartridges and accessories, not peptides. Every pen comes with an empty 3 mL cartridge, ready for you to fill.

### Can I use one pen for different peptides?

Yes. You can swap cartridges in and out of one pen; just re-prime each time you swap. Or keep one pen per peptide and tell them apart with [pen labels](/product/peptide-pen-labels) and colored [Halo cartridge holders](/product/halo-cartridge-holder).

### How many units are in a 3 mL cartridge?

300. One click is one unit, and one unit is 0.01 mL, so a full 3 mL cartridge holds 300 units. How many doses that gives depends on your dose size; the [peptide pen dosage calculator](/peptide-calculator) works it out.

### Is a RefillPen the same as a reusable insulin pen?

It works the same way: a mechanical pen with a dose dial that takes standard 3 mL cartridges and screw-on pen needles, with no batteries. RefillPen is made and sold for peptides, in four models and 50 color combinations.

### How should I store and travel with a loaded pen?

Never leave a pen or cartridges in a car, even covered: it can pass 86 °F within minutes. When flying, keep the pen and supplies in your carry-on, because a checked bag’s hold can freeze. Take the needle off after every use. The [FAQ](/faq) covers storage and travel in more detail.

### Do you ship RefillPen to the UK?

Yes. We ship internationally by USPS, including to the United Kingdom, at a flat rate shown in your cart. See [Shipping & Delivery](/shipping) for every country.

### Which reusable peptide pen should I choose?

Choose the V1 if you need the widest range (up to 80 units), the V3 for a solid metal closed-cap pen, or the V2.5 Slim Hybrid for a lighter body that keeps the needle hidden. The [Best Reusable Peptide Pen guide](/best-reusable-peptide-pen) compares them side by side.