Full unit(s) can also be described as "even units", meaning there are no fractions (example: 1 1/21 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 halfunit 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 commonlyavailable 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 equal1 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.
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 lowdose 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 nonnumbered 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 halfunit scale or halfscale markings, as seen here, ^{[5]} in the photo above, and in this table.
U100 Syringe Sizes  

1cc (1 ml) Syringe  
Holds maximum:  100 units ^{[6]} 
Numbered in:  10 unit increments ^{[6]} 
Smallest line measures 2 units: ^{[7]}  BD ^{[6]} ReliOn ^{[8]} Monoject ^{[3]} (all but 31 gauge needle) 
Smallest line measures 1 unit:  Easy Touch ^{[9]} Precision Sure Dose ^{[3]} UltiCare ^{[3]} Monoject ^{[3]} (31 gauge needle only) 
1/2cc (0.5 ml) Syringe  
Holds maximum:  50 units ^{[10]} 
Numbered in:  10 unit increments ^{[10]} 
Smallest line measures 1 unit: ^{[7]}  BD ^{[10]} Precision Sure Dose ^{[3]} UltiCare ^{[4]}^{[3]} Easy Touch ^{[9]} ReliOn ^{[8]} Monoject ^{[3]} 
3/10cc (0.3 ml) Syringe  
Holds maximum:  30 units ^{[11]} 
Numbered in:  5 unit increments ^{[11]} 
Smallest line measures 1 unit: ^{[7]}  BD Micro Fine ^{[3]} BD Ultra Fine ^{[11]}^{[3]} (standard length only) Monoject ^{[3]} Easy Touch ^{[9]} UltiCare ^{[3]} 
Halfunit scale 3/10cc (0.3 ml) Syringe ^{[5]}  
Holds maximum:  30 units ^{[11]} 
Numbered in:  5 unit increments ^{[11]} 
Smallest line measures 1/2 unit:  BD Ultra Fine II (short) ^{[11]}^{[3]} ReliOn ^{[8]}^{[3]} 
All U40 syringes have their markings at one unit; there are none marketed with halfscale, or half unit markings.
U40 Syringe Sizes  

2cc (2ml) Syringe ^{[12]}  
Holds maximum:  80 units 
Numbered in:  5 unit increments 
Smallest line measures:  1 unit 
Barrel Markings in:  Red: Caninsulin ^{[13]} 
1cc (1ml) Syringe  
Holds maximum:  40 units 
Numbered in:  5 unit increments 
Smallest line measures:  1 unit 
Barrel Markings in:  Red: BD, Caninsulin Black: Vetsulin, UltiCare color ?: MVP ^{[14]}^{[15]} 
1/2cc (0.5ml) Syringe  
Holds maximum:  20 units 
Numbered in:  5 unit increments 
Smallest line measures:  1 unit 
Barrel Markings in:  Red: BD, Caninsulin Black: Vetsulin, UltiCare color ?: MVP ^{[14]}^{[15]} 
3/10cc (0.3ml) Syringe ^{[16]}  
Holds maximum:  12 units 
Numbered in:  5 unit increments 
Smallest line measures:  1 unit 
Barrel Markings in:  Black: UltiCare 
If a dosage looks wrong to you, DON'T BE AFRAID to ask someone for helpyour vet, an animal emergency clinic, or a canine ^{[17]} diabetes message boardBEFORE 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 wellbeing or appetite. Tell owners to offer food immediately if the pet is weak or is behaving strangely." 

and rounded down to whole number 
rounded down to nearest whole or half unit ^{[20]} 
Weight pounds  Weight kilos  Starting Dose Range 

05 lb  02 kg  0.501 IU 
10 lb  04 kg  12 IU 
15 lb  06 kg  1.53 IU 
20 lb  09 kg  24 IU 
25 lb  11 kg  2.55 IU 
30 lb  13 kg  36 IU 
35 lb  15 kg  3.57 IU 
40 lb  18 kg  4.59 IU 
45 lb  20 kg  510 IU 
50 lb  22 kg  5.511 IU 
55 lb  25 kg  612 IU 
60 lb  27 kg  6.513 IU 
65 lb  29 kg  714 IU 
70 lb  31 kg  7.515 IU 
75 lb  34 kg  8.517 IU 
80 lb  36 kg  918 IU 
85 lb  38 kg  9.519 IU 
90 lb  40 kg  1020 IU 
95 lb  43 kg  10.521 IU 
100 lb  45 kg  1122 IU 
ReferencesEdit
 ↑ Using Caninsulin/Vetsulin with U100 syringesPage 2. Intervet.
 ↑ Milliliters to cubic centimeters. Metric Conversions.org.
 ↑ ^{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.
 ↑ ^{4.0} ^{4.1} UltiCare U100 SyringesProduct Information.
 ↑ ^{5.0} ^{5.1} Comparison of 3/10 cc syringe markshalf unit and whole unit scale. BD Diabetes.
 ↑ ^{6.0} ^{6.1} ^{6.2} Closeup of BD 1cc SyringesUltraFine30 Gauge1/2", UltraFine II Short31 Gauge5/16" & MicroFine28 Gauge1/2".
 ↑ ^{7.0} ^{7.1} ^{7.2} Diabetes Mellitus. Washington State University.
 ↑ ^{8.0} ^{8.1} ^{8.2} ReliOn Insulin Syringe Markings.
 ↑ ^{9.0} ^{9.1} ^{9.2} Easy Touch Syringe demonstrationtheir syringes all measure in 1 unit increments.
 ↑ ^{10.0} ^{10.1} ^{10.2} Closeup of BD 1/2 cc SyringesUltraFine30 Gauge1/2", UltraFine II Short31 Gauge5/16" & MicroFine28 Gauge1/2".
 ↑ ^{11.0} ^{11.1} ^{11.2} ^{11.3} ^{11.4} ^{11.5} Closeup of BD 3/10 SyringesUltraFine30 Gauge1/2", UltraFine II Short31 Gauge5/16", UltraFine ShortHalf Unit Markings31 Gauge5/16" & MicroFine28 Gauge1/2".
 ↑ Caninsulin 2ml syringes sold in the UK.
 ↑ Caninsulin 2 ml syringesUK.
 ↑ ^{14.0} ^{14.1} MVP U 40 syringe.
 ↑ ^{15.0} ^{15.1} Easy Touch/MVP Vet Syringes.
 ↑ U40 3/10cc Syringes. VetRxSupply.
 ↑ K9 Diabetes Forum
 ↑ Cook, Audrey (2007). Latest Management Recommendations for Cats and Dogs with Nonketotic Diabetes Mellitus. DVM 360.
 ↑ Cook, Audrey (2007). What Clients Need to Know. DVM 360. Archived from the original on 20120717.
 ↑ Pounds to Kilograms/Kilograms to Pounds online converter. Open Toronto.
More InformationEdit
 Milliliter to Cubic Centimeter Converter CalculateMe.com