Vial sizes: 5 mg or 10 mg, and per-mg cost
Why larger vials cost less per mg, how to choose a size for the work in hand, and the trade-off with reconstituted shelf life and batch consistency.
Alphex peptides come in two or four vial sizes, and the per-mg price falls as the vial gets larger. Choosing the size is a small decision with a real effect on both cost and how much material ends up discarded. This note explains why larger vials are cheaper per mg, how to choose a size for the work in hand, and the trade-off between per-mg saving and reconstituted shelf life. All Alphex products are for laboratory and in-vitro research only.
Why per-mg cost falls with vial size
Most of the cost of a vial is fixed regardless of what is in it: the vial, stopper and crimp; filling and freeze-drying; labelling; a share of the batch's independent testing; packing and dispatch. The peptide itself is a smaller fraction of the price than buyers assume, especially for short, easily synthesised sequences. So a 10 mg vial costs considerably less than twice a 5 mg vial, and a 30 mg vial of GLP-3 (RT) is well under six times the 5 mg price. See how peptide pricing works.
Sizes in the catalogue
- BPC-157: 5 mg, 10 mg
- TB-500: 5 mg, 10 mg
- GHK-Cu: 50 mg, 100 mg (larger, because typical in-vitro and formulation work uses more)
- Ipamorelin: 5 mg, 10 mg
- GLP-3 (RT): 5 mg, 10 mg, 20 mg, 30 mg
- Bacteriostatic water: 10 mL
Live prices per size are on each product page; the per-mg comparison is a matter of dividing.
Choosing a size
- Estimate total peptide the project needs. Number of experiments times material per experiment, plus a margin for repeats and pilot runs.
- Consider reconstituted shelf life. A reconstituted stock lasts weeks refrigerated or months as frozen aliquots. If a 10 mg vial's stock would sit for six months, two 5 mg vials opened three months apart may waste less. See how long reconstituted peptides last and aliquoting.
- Consider concentration. A larger vial reconstituted in the same volume gives a more concentrated stock, which is more stable and less prone to adsorption losses; dilute working solutions are made fresh. See adsorption.
- Consider batch consistency. One larger vial guarantees a single batch for the whole project; two smaller vials bought months apart may be different batches. If batch consistency matters, buy the project's requirement together, from one batch, and aliquot.
- Pilot work: the smallest size. Repeated or multi-arm work: the largest size the shelf-life rule allows.
The unopened-vial rule
Sealed vials keep for years at -20 C. So the calculation is about opened vials, not purchased ones: buying several small vials and opening them one at a time gives you the batch consistency of a large purchase with the shelf life of a small one, at a slightly higher per-mg cost. For many laboratories that is the right compromise. See long-term storage.
Frequently asked questions
Is the peptide in a 10 mg vial the same as in a 5 mg vial?
Same batch, same specification, same COA; only the fill mass differs.
Why does GLP-3 (RT) come in larger sizes than the others?
Because it is expensive to hold and typically used in larger quantities per experiment; the 20 mg and 30 mg sizes carry the lowest per-mg cost. See the GLP-3 (RT) guide.
Can I order a size not listed?
Not from stock; ask about departmental requirements via bulk and repeat orders.
Alphex research peptides are supplied for laboratory and in-vitro research by qualified researchers only. They are not authorised for human or veterinary use.
Research use only. Alphex products are supplied exclusively for laboratory and in-vitro research by qualified researchers. They are not authorised for human or veterinary use, and nothing in this note is advice on any such use.
Published 29 April 2026. Alphex reviews research notes when the testing method, the catalogue or UK guidance changes.