Insulin Syringe Sizes for Peptides: U-100 Explained

Reference guide. Next Day Pharma supplies pre-filled, ready-to-use injection pens — there is nothing to mix, and no vials, powder or bacteriostatic water are involved. This article is published as general reference information only.

Most peptide use uses standard U-100 insulin syringes. Here is what that means and which size to pick.

What U-100 means

A U-100 syringe is graduated so that 100 units equals 1 ml. It is the global standard for insulin and for peptide dosing because it gives 1-unit precision (0.01 ml).

Common capacities

Size	Capacity	Best for
0.3 ml	30 units	Microdoses
0.5 ml	50 units	Standard low-mid doses
1.0 ml	100 units	Higher doses, fewer injections

Needle gauge and length

29G–31G, 8–13 mm is the standard for subcutaneous injection. Shorter is more comfortable; longer reaches deeper if you have higher subcutaneous fat.

UK supply

Pharmacies sell U-100 insulin syringes over the counter in the UK. They are inexpensive and there is no good reason to reuse them.

Frequently asked questions

Can I use a tuberculin syringe instead?

You can but graduation in 0.01 ml steps is less convenient than insulin "units".

How many syringes per vial?

One per injection. Never reuse — sterility matters.

Where do I buy them?

Any UK pharmacy. Next Day Pharma supplies pre-filled pens, so no separate syringes are needed for our products.

This guide is provided for informational purposes by Next Day Pharma. All peptides supplied are FOR RECONSTITUTION. Always consult a qualified healthcare professional before use.

Peptide catalogue

Melanotan II — £40.00 — 10mg of Melanotan II
Somatropin (HGH) — £60.00 — Somatropin (Human Growth Hormone)
Cagrilintide 10mg — £60.00 — 10mg of Cagrilintide
Epitathlon — £50.00 — 10mg of Epitathlon
PT-141 10mg — £40.00 — 10mg of PT-141
SLU-332 5mg — £65.00 — 5mg of SLU-332
CJC + Ipamorelin — £55.00 — 5mg CJC-1295 + 5mg Ipamorelin
5 Amino 1MQ 50mg — £60.00 — 50mg of 5 Amino 1MQ
SS-31 10mg — £40.00 — 10mg of SS-31
Semax 10mg — £40.00 — 10mg of Semax
Selank 10mg — £40.00 — 10mg of Selank
Ipamorelin 10mg — £40.00 — 10mg of Ipamorelin
Wolverine — £75.00 — 10mg of Wolverine
MOTS-C 20mg — £80.00 — 20mg of MOTS-C
Tesamorelin 20mg — £110.00 — 20mg of Tesamorelin
NAD+ 1000mg — £125.00 — 1000mg of NAD+
GLO 70mg — £70.00 — 70mg of GLO
KLOW 80mg — £90.00 — 80mg of KLOW
BPC-157 10mg — £40.00 — 10mg of BPC-157
TB500 10mg — £50.00 — 10mg of TB500
Retatrutide — £200.00 — Retatrutide
Tirzepatide — £180.00 — Tirzepatide
MT2 10mg (NEXT DAY TAN) — £50.00 — 10mg of Melanotan2
GHK-CU 100mg — £60.00 — 100mg of GHK-CU

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Tirzepatide side effects — What appears when, how long it lasts and what actually helps.
Retatrutide side effects — Why titration speed matters most, and how to manage the first days after a dose.
Where to buy Retatrutide in the UK — Supplier checklist, real pricing, pens vs powder, dosing and next-day tracked delivery.
Where to buy Tirzepatide in the UK — What to check in a UK supplier, how pens compare on cost, and the standard titration schedule.
Where to buy Melanotan 2 in the UK — Buying MT2 safely in the UK, loading vs maintenance dosing, and what to expect week by week.
Where to buy PT-141 in the UK — PT-141 (Bremelanotide) explained: UK supply, timing, typical doses and common questions.
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BPC-157 dosage guide — Typical daily amounts, timing and cycle length for BPC-157.
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Where to buy GHK-Cu in the UK — Copper peptide for skin, hair and recovery: amounts, cycling and storage.
Where to buy TB-500 in the UK — Loading and maintenance amounts, and how TB-500 compares with BPC-157.
Where to buy 5-Amino-1MQ in the UK — Fat loss without appetite suppression: how NNMT inhibition differs from GLP-1s.
How to use a pre-filled peptide pen — Step by step for a first dose: dialling, sites, the ten-second hold and sharps disposal.
What to do if you miss a dose — How late is too late, when to skip, and coming back after a break.
Travelling with peptide pens — Airport security, cool bags, hotel fridges and how long pens last out of the fridge.
How to store peptide pens in the UK — Fridge temperatures, in-use windows, travelling and what to do after a delivery delay.
Free peptide dosage calculator — Work out doses and volumes for the most common peptides.
Dosage and titration guide — Find the pen strength that matches your weekly dose.