Insulin Syringe Guide for Peptide Research: U-100 Units to mL Conversion
Published: 2026-08-03 · Last updated: 2026-08-03
The insulin syringe is the most common tool in a peptide research setup, and it is also the one people misread most often. The units on the barrel are borrowed from diabetic medicine and only make sense once you know the conversion. This guide walks through the U-100 convention in plain English, shows you how to convert units to millilitres without doing long division, and covers what to actually buy at a Canadian pharmacy.
Why insulin syringes for peptide work?
Insulin syringes were designed for one specific job: delivering very small volumes of a very concentrated drug (insulin at 100 units per mL) with fine precision. Every property that makes them good at insulin — small barrel volume, tight tick marks, thin needle, short needle length — happens to make them ideal for reconstituting research peptides and drawing small aliquots.
A 1 mL insulin syringe has 100 clearly-marked units on the barrel. That is 10 times more divisions than the "0.1 mL" ticks on a generic tuberculin syringe of the same volume. When you are working with a peptide at, say, 5 mg per mL and you want to draw 50 micrograms, the difference between reading 1 unit and reading 0.01 mL is night and day.
The other reason: short needles. A standard insulin syringe comes with a 5/16-inch (roughly 8 mm) or 1/2-inch (12.7 mm) needle. That is short enough to fit inside a small vial without hitting the far side of the glass, which matters when you are drawing from a 3 mL peptide vial. Longer needles are unnecessary for reconstitution and aliquoting.
What does U-100 mean in practice?
U-100 is a labelling convention: the syringe barrel is calibrated on the assumption that every 100 units on the barrel corresponds to 1 mL of fluid. This is baked into the manufacturing — it is not something you can adjust. If your syringe box says "U-100," 100 ticks equals 1 mL.
For peptide research, ignore the word "insulin" and just treat the barrel as a fine-grained millilitre scale. One unit is 0.01 mL. Ten units is 0.1 mL. Fifty units is half a millilitre. One hundred units is a full millilitre. That is the entire conversion table.
Where people get in trouble is when they see a peptide dosing protocol written in micrograms or milligrams and try to read it directly on the syringe. The syringe measures volume, not mass. You have to know your peptide concentration (mg per mL, from reconstitution) to translate a mg dose into a mL volume, and only then into units. Our reconstitution basics guide walks through that math.
How do I convert units to mg for a given peptide?
Two steps. First, work out the concentration from your reconstitution: total mg in the vial divided by total mL of bacteriostatic water you added. For a 10 mg vial with 2 mL of water, that is 5 mg per mL.
Second, divide that concentration by 100 to get mg per unit. 5 mg per mL divided by 100 units per mL = 0.05 mg per unit. So every unit on the syringe is 50 micrograms of peptide, every 10 units is 500 micrograms, and every 20 units is 1 mg. Once you have written that conversion on the vial label, you never have to do the math again for that vial.
A different vial size or reconstitution volume changes the numbers but not the process. Always: work out mg/mL, then divide by 100 to get mg/unit, then multiply by whatever unit count you want to draw. This is where a labelled vial saves your life — writing "5 mg/mL, 50 mcg/unit" on the vial in permanent marker takes ten seconds and removes an entire class of downstream mistakes.
What needle gauge and length should I buy?
For research peptide work in Canada, the common sensible choice is a 29 or 30 gauge needle, 5/16 inch long. Higher gauge means thinner needle. Thinner needle means less coring of the rubber stopper, less dead space, and gentler passage through the vial seal. There is very little downside to going finer.
Length is a matter of vial geometry. Short needles (5/16 inch) fit any standard peptide vial comfortably. Longer needles (1/2 inch or more) exist for injection use cases that do not apply to lab work — for reconstitution and aliquoting, they just get in the way. A 5/16 inch, 30 gauge, 1 mL U-100 barrel is the most common sensible default.
If you need to draw larger volumes for aliquoting — say, splitting a 3 mL master into multiple 0.5 mL tubes — a 3 mL insulin syringe is a variant that exists and can be handy. The barrel is longer and marked to 300 units. Same U-100 convention, just more capacity.
Where do Canadians buy insulin syringes?
Every Canadian pharmacy carries them. They are typically behind the counter, so you ask the pharmacist by name — "a box of U-100 insulin syringes, 30 gauge, 5/16 inch, 1 mL." A box of 100 is the most common pack size and usually costs under CAD $30. No prescription needed in most provinces, though the pharmacist may ask what you are using them for; a straight "research use" answer is enough.
Chain pharmacies like Shoppers Drug Mart, Rexall, and London Drugs all stock them. So do most independent pharmacies. If your local shop is out, they can usually order in a box within a couple of business days. Online medical suppliers (like Amazon.ca Business or Medex) also sell them, but the pricing is rarely better than the pharmacy behind the counter.
Prescott Bio does not sell syringes — pharmacy sourcing is easier for everyone. What we do carry is bacteriostatic water when it is in stock; see our bacteriostatic water guide and the peptide catalogue for current inventory.
How do I dispose of used syringes?
Not in the household trash. Used needles are sharps and need to go in a proper sharps container. You can buy small sharps containers at any pharmacy for a few dollars — they look like a bright red or yellow plastic tub with a one-way lid. Drop your used syringes in as you go.
When it is full, most Canadian pharmacies take back sharps containers for safe disposal free of charge. Ask at the counter where you bought it. Some municipalities also run sharps return programs at community health centres. Do not throw a full sharps container in the recycling or the garbage — needle-stick injuries to sanitation workers are a real problem.
If you are working through a lot of syringes and reconstitutions, keep the sharps container on the same bench where you work. The moment you have to walk across the room to dispose of something is the moment you cap-and-forget, and cap-and-forget is how you end up with used needles in surprising places.
Questions Canadian buyers ask
What does U-100 actually mean?
U-100 is a labeling convention that says the syringe barrel is marked in "units" where 100 units equals 1 millilitre. It was designed for insulin, which comes in U-100 concentration. For peptide research, we borrow the syringe because the fine markings are useful — the "insulin units" become a convenient way to read fractions of a millilitre.
How do I convert units to mL?
One unit on a U-100 syringe is 0.01 mL, or 10 microlitres. So 10 units = 0.1 mL, 50 units = 0.5 mL, 100 units = 1.0 mL. Every 10 units is one-tenth of a millilitre. This is the only conversion you need to memorise.
What needle gauge should I use?
For drawing from vials and gentle handling, 29 to 31 gauge is standard. The higher the gauge number, the finer the needle. Fine needles are less likely to core a vial stopper. If you are only using the syringe for reconstitution and aliquoting, gauge matters less than needle length — short needles (5/16 inch, sometimes called 8 mm) are easier to manoeuvre.
Where do I buy insulin syringes in Canada?
Any Canadian pharmacy sells them behind the counter — you ask the pharmacist for U-100 insulin syringes in the size you want. No prescription is needed in most provinces, though the pharmacist may ask what you are using them for. Boxes of 100 are the most common size.
Can I reuse an insulin syringe?
No. Needles dull after one use, which increases the chance of coring the vial stopper and drops solvent contamination back into the vial. Syringes are cheap, sterile, and disposable — use one, drop it in a sharps container, grab a fresh one next time.