U100syringe U40insulin

Units as measured in a U 40 syringe (top) and a U 100 syringe (bottom).

The (International Unit=IU) measurement used to calculate and measure dosages of insulin. Each unit of insulin is expected to have a particular medical effect on the subject.

Full unit(s) can also be described as "even units", meaning there are no fractions (example: 1 1/2--1 1/4) involved. In most adult humans, a difference of 1 full unit is roughly the smallest amount that makes a significant repeatable clinical difference in dosage.

The smaller the patient, the more chance you will need to deal with dosages having fractions in them. An example is found in children, who are smaller and need less insulin than adults; many find the 3/10 syringes with half-unit markings a great help with drawing children's insulin. Cats are normally about 1/10 the body weight of humans; most dogs' weight lies along the range between cats and children.

Insulin dosage is often specified (to vets and doctors only) in terms of units/kg body weight. In humans and dogs this is a common way to calculate a rough target dose (though individual cases will differ and dosing should always begin conservatively!).

Measurement of insulin in syringes is based on the cubic centimeter (cc) volume measurement system for injectable liquid medications. Your box of syringes is labeled as to how many cc's a syringe will hold. U100 and U40 syringes labeled as 1cc will each hold one cubic centimeter (ml) of liquid, although as the insulin strength is increased, more units will be packed into one cc. A cc (holding a milliliter of liquid) contains 40 Units of U40 insulin, 50 Units of U50 insulin, or 100 Units of U100 insulin.

It is possible, though usually not recommended, to dose U40 insulin in a U100 syringe. [1] Be careful to convert the right way. See this table.

With so many abbreviations, one can sometimes get confused. An easy way to separate units (IU) from milliliters (ml) is to think about the following: all commonly-available vials of insulin approved for humans are 10ml vials. Most insulin cartridges for refillable pens contain 3 ml of insulin each. Caninsulin/Vetsulin comes in both a standard 10ml vial and a pack of 10 2.5ml vials. Since a U100 1cc syringe holds 1 milliliter of liquid, drawing this amount from the insulin vial would fill the syringe with 100 units of insulin; that would also be 1/10 of an entire 10ml vial and 1/3 of a 3ml insulin cartridge; it would be more than 1/3 of a 2.5 ml Caninsulin or Vetsulin vial.

Milliliters and cubic centimeters (cc) are equal-1 milliliter=1 cubic centimeter or cc, [2] so there's enough insulin in a new 10ml vial to fill a 100 IU (1 cc) insulin syringe ten times. If you look at the starting dose tables for an animal weighing 100 pounds, the most units of insulin you would be giving when starting out would be 22 units.

3 10

3/10 cc U 100 insulin syringe holds a maximum of 30 IU's of insulin.

The syringe in this photo is a 3/10 syringe (this is the smallest size insulin syringe there is; the 3/10 cc syringes are often referred to as low-dose syringes) holding at most, 30 units of insulin. To give a 100lb animal 22 units of insulin, you wouldn't even fill it totally up; 22 units is between the numbers 20 and 25. You'd still have 8 units worth of "room" left in the syringe.

If for any reason you need to change the size of the U100 syringe you normally use, extra care at drawing insulin will be needed. Those normally using 3/10 cc syringes, with single or half unit markings, could risk giving too much insulin by following the mark on 1cc syringes. Some brands of 1cc syringes have their smallest non-numbered marks at 2 units, [3] others have theirs at 1 unit. [4]

The 1/2cc syringe has 1 unit marks. Some manufacturers have 3/10cc syringes with 1 unit marks and some with 1/2 unit marks referred to as half-unit scale or half-scale markings, as seen here, [5] in the photo above, and in this table.

All U40 syringes have their markings at one unit; there are none marketed with half-scale, or half unit markings.

If a dosage looks wrong to you, DON'T BE AFRAID to ask someone for help--your vet, an animal emergency clinic, or a canine [17] diabetes message board--BEFORE you give an injection of a questionable dose. Delaying a shot if you're not sure is much safer than the alternative.

From the DVM 360 2007 article by Dr. Audrey Cook: [18][19]

"Hypoglycemia is deadly; hyperglycemia is not. Owners must clearly understand that too much insulin can kill, and that they should call a veterinarian or halve the dose if they have any concerns about a pet's well-being or appetite. Tell owners to offer food immediately if the pet is weak or is behaving strangely."

Insulin Starting Doses
Pounds converted to kilos
and rounded down to whole number
Insulin doses based on 0.25-0.50 IU per kilo,
rounded down to nearest whole or half unit [20]


  1. Using Caninsulin/Vetsulin with U-100 syringes-Page 2. Intervet.
  2. Milliliters to cubic centimeters. Metric
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 Diabetes Health Syringe Listings.
  4. 4.0 4.1 -Ulti-Care U100 Syringes-Product Information.
  5. 5.0 5.1 Comparison of 3/10 cc syringe marks-half unit and whole unit scale. BD Diabetes.
  6. 6.0 6.1 6.2 Close-up of BD 1cc Syringes-UltraFine-30 Gauge-1/2", UltraFine II Short-31 Gauge-5/16" & MicroFine-28 Gauge-1/2".
  7. 7.0 7.1 7.2 Diabetes Mellitus. Washington State University.
  8. 8.0 8.1 8.2 ReliOn Insulin Syringe Markings.
  9. 9.0 9.1 9.2 Easy Touch Syringe demonstration-their syringes all measure in 1 unit increments.
  10. 10.0 10.1 10.2 Close-up of BD 1/2 cc Syringes--UltraFine-30 Gauge-1/2", UltraFine II Short-31 Gauge-5/16" & MicroFine-28 Gauge-1/2".
  11. 11.0 11.1 11.2 11.3 11.4 11.5 Close-up of BD 3/10 Syringes-UltraFine-30 Gauge-1/2", UltraFine II Short-31 Gauge-5/16", UltraFine Short-Half Unit Markings-31 Gauge-5/16" & MicroFine-28 Gauge-1/2".
  12. Caninsulin 2ml syringes sold in the UK.
  13. Caninsulin 2 ml syringes-UK.
  14. 14.0 14.1 MVP U 40 syringe.
  15. 15.0 15.1 Easy Touch/MVP Vet Syringes.
  16. U-40 3/10cc Syringes. VetRxSupply.
  17. K9 Diabetes Forum
  18. Cook, Audrey (2007). Latest Management Recommendations for Cats and Dogs with Nonketotic Diabetes Mellitus. DVM 360.
  19. Cook, Audrey (2007). What Clients Need to Know. DVM 360. Archived from the original on 2012-07-17.
  20. Pounds to Kilograms/Kilograms to Pounds online converter. Open Toronto.

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