Diabetes in Pets

Close-up illustration of a syringe needle showing bevel, point and heel.

Syringes[1] are commonly used to inject cats and dogs with insulin. The strength of an insulin is measured in International Units (IUs)[2]. The two common strengths are U40 and U100, meaning 40 units and 100 units per millilitre, respectively. Cubic centimeters (cc's) and milliliters (mL's) are interchangable, so syringes marked 1ml equals 1cc; 0.5 ml equals 1/2cc. 3/10cc equals 0.3ml[3].

There are syringes designed for use with U100 insulin and syringes designed for use with U40 insulin. They were at one time color-coded: U100 syringes having orange caps while U40's have red ones[4][5]. Unfortunately some U40's now have orange caps, too -- check the barrel carefully for U40 or U100 to be sure!

Syringe use[]

To inject, pull skin up first, and insert the needle firmly parallel to the body, bevel side up[6].


Correct way to give an injection when "tenting" the skin. This makes sure the insulin is injected into the skin flap created by "tenting" it. When the skin "tent" is released, the injected insulin is under it, or subcutaneous.


Wrong way to give a shot: The needle has totally passed through the "tented skin". The insulin, or any other injected drug, will be injected into the air. Note that in this graphic, the injection point is much closer to the "pinch" area holding the "tent" up. In the correct graphic, the injection point is closer to the body.

Insulin syringes are intended for a single use only. Using them twice[7] may contaminate and/or interfere with some insulin's activity, in addition to wearing the protective coating off the needle and causing more pain at injection[8]. When the protective silicon coating is worn away by re-use, it can also contaminate the insulin; white precipitates[9]can form in the vial from the silicon, possibly interfering with the action of the insulin[10].


Insulin syringe needles. Image 1, never used. Image 2, used once. Image 3, used twice. Image 4, used six times.

Comparing the first use and the sixth use in the photo examples, you can see how the coating has almost been totally worn off by the sixth use. You can also see the point beginning to blunt after second use. When a needle becomes blunted from re-use as you see in the photos, it can create lipohypertrophy due to skin damage[11]. Injecting insulin into areas like this means poor or slow insulin absorption. Some people use yesterday's syringe or disposable needle as a lancet, though.

NeedleBevels svg

This shows the common bevels for syringe needles. The one used on insulin syringes and insulin pen needles is the one at the top-standard bevel.

You can also see that when the needle is held with the bevel side up (facing toward you, not the patient), the bevel is angled to slide under the skin, meaning less pain at injection.

If you should bend a needle while drawing insulin, discard the syringe and start again; don't try to straighten it out[12]. Inserting the needle all the way into the vial makes it less easy to bend[13].

Injection Helpers[]

  • If you feel all thumbs when giving shots or think you need more than two hands when giving them, BD's Inject-Ease may be just what you need. The device holds a filled BD insulin syringe (Micro-Fine or Ultra-Fine BD brands). Inject-Ease inserts the needle into the skin and delivers the injection at the touch of a button. You may need to have your pharmacy order[14] this for you. It's a big help with both small children and pets needing insulin shots. It has been used with success for some CDMB dogs who were difficult at injection time. BD shows the Inject-Ease on their syringes page for dogs[15]and cats[16].
  • Magni-Guide[17] by BD, is both magnifies the syringe barrel scale markings and can help steady the vial and syringe while drawing insulin. The device is designed to work with Lilly insulin vials. One can use Sanofi-Aventis (Lantus, Apidra) insulins with it, but the fit is loose so the vial must be assisted by the user's hands; Novo Nordisk vials also fit Magni-Guide, but very tightly--they may even crack the device.

Drawing Insulin[]

  • Do NOT wipe the needle with alcohol as it removes the protective coating. This coating is what makes injection easier and less painful.[18].
  • To eliminate bubbles: If drawing insulin from a vial, set the syringe plunger to the dosage you want to draw, put the needle into the top of the vial while the vial is still upright, and push all the air out of the syringe. This will maintain air pressure equilibrium in the vial once you draw the dose and, because the vial is upright, will not cause air bubbles to mix with the solution. Turn the vial upside down and draw the insulin slowly.
  • If you do get air bubbles into the syringe, it's ok with most insulins to re-inject the insulin into the vial and draw again until the air is gone[19]. Check that this is ok with your insulin. See also injecting insulin. Slower draw is less likely to draw bubbles.
  • Another way to get rid of syringe air bubbles is to hold the syringe upright and give it a tap or two with your finger. The problem with having air bubbles in the injection is that you will not be getting the full dose of insulin; the bubbles take the place of it[20].
  • Some people prefer to gently jiggle their vials to make any air bubbles rise to the top, away from where the needle will draw[21].
  • Some caregivers find that certain syringe brands are less susceptible to air bubbles than others because they have a smoother push and pull motion. If you consistently have problems with air bubbles, consider trying other syringe brands.

Measuring dose[]


Right and wrong way to measure insulin units in a syringe. Using the back section of the rubber plunger as a guide will result in underdosing; the rubber plunger is solid-the drawn insulin is only in front of it. Measure from the front section of the plunger--the one closest to the needle area.

Some people find that dose differences as small as 0.1 units make a difference. Since a cat or small dog weighs 1/10 what a human does, it may easily be the case. If 0.2 units and 0.3 units actually seem to give a different result in your cat or small dog, you may find it useful to try half-unit marked syringes. This guide shows how to read fine doses of 0.1 through 0.5 units.[22]

  • For very fine doses (less than half a unit increments), some people have tried:
    • Using a magnifier.
    • Diluting the insulin (this must be done with the correct diluent and usually is done by a pharmacist.)
    • Using a U100 syringe with U40 insulin and converting (see Conversion below).
    • Experimenting with the size of droplets they can coax from a syringe, learning those sizes, and measuring them against fractional unit sizes.
    • Learning to eyeball fine doses down to 0.1 units[23].
    • Plungers may be pushed or pulled with a "screwing" motion for finer control of partial units.

Prefilling tips[]

There are times when you may want to prefill a syringe with a known dose and leave it for yourself or someone else to use later. If doing so, keep in mind:

  • Recap the needle with great care -- needles can easily go through the side of the cap into your fingers.
  • Store the recapped needle point-up to avoid clogging the needle.
  • If the insulin needs refrigeration normally, so do the prefilled syringes.
  • The "cloudy" insulins (NPH, Lente/Ultralente, PZI, Mixes) need to be re-suspended before use. Gently roll the syringe back and forth in your hands as with the vial. Improperly suspended insulin may lose some or all of its effectiveness.
  • Some insulins, including Lantus and Vetsulin, will react with the syringe's inner coating over time and lose effectiveness, or even lose their time-delay action. Check with your insulin manufacturer if prefilling syringes is permitted.
  • According to Novo Nordisk[24], prefilled syringes containing any of their Novolin, Actrapid, Insulatard, Actraphane, and Mixtard insulins can be kept refrigerated for 30 days. Eli Lilly says any of their Humulin insulins in prefilled syringes are good for 21 days when refrigerated.

Buying syringes[]


Common brands of U100 syringes are BD[25] and Monoject[26].

  • The Children With Diabetes page link below[27] has links to syringe brand comparisons.
  • The page linked below[28]gives an overview of all BD syringe types with clickable photos that enlarge.
  • Wal-Mart[29] has a house brand of syringes, ReliOn, that compare to BD syringes in everything except price[30]. The page below[31] has a clickable photo that enlarges for better comparison of the BD syringe and the ReliOn[32]. Wal-Mart also has ReliOn/Novolin branded insulins, which are made for them by Novo Nordisk. The only difference here also is in the price.
  • Precision Sure-Dose syringes are made by Terumo[33][34] marketed by Abbott. They compare favorably to BD, but cost quite a bit less. The link below[35] describes all available models and has a clickable photo that enlarges for a better look[36]. CVS pharmacies in the US stock and offer Precision syringes.
  • Ulti-Care[37] offers U100 syringes with barrel sizes 3/10 cc (no 1/2 unit markings), 1/2 cc, and 1 cc with a variety of needle gauges from 28-31. Its 28 and 29 gauge syringes have a 1/2" needle while its 30 and 31 gauge syringes have a 5/16" needle. Factoring in shipping, the prices are about equal to buying syringes offline. No prescription is needed to purchase syringes from UltiCare; it is located in Minnesota where no state law requires it. Shipping within the US only.
  • Comparison chart showing all types of U100 insulin syringes sold in the US[38]

Retailers on-line[]

  • Hocks.com[39] offers a broad range of U100 syringes at reasonable prices. Shipping within the US only.
  • Diabetic Promotions[40] offers another large selection of syringes and supplies, and will ship to Canada and worldwide.

Prescription Laws[]

Some countries require a prescription[41] for insulin syringes and/or pen needles.

Rx Needed-Countries[42]


No Rx Needed-Countries[43]

Costa Rica
New Zealand
May need to show proof of diabetes
May need to show proof of diabetes

In the US, whether or not you need a prescription for syringes/pen needles is determined by state, not US, law. The laws of your state will apply re: syringes/pen needles requiring a prescription. If you order syringes or pen needles online, the law of the state where you're ordering them from will apply. If you order from a business whose state does not require a prescription for syringes or pen needles, you will not need one, even if the laws of your state of residence says you do. Conversely, if you live in a state where there's no mandatory prescription for syringes or pen needles and order from a company in a state where a prescription is necessary, you will need one to do business with them.

Any pharmacy may have its own policy regarding a precription being necessary or not[44]. It's best to ask before you place an online order if the store's policies aren't clearly stated or make a trip to the brick and mortar pharmacy.

U100 Syringes[]

Disposable Insulin Syringe

U100 insulin syringe.

U100-concentrated insulin has 100 units per ml of liquid, and should be used with U100 syringes.

Because U100 insulin syringes are designed for human use, they are available from brick-and-mortar or Internet pharmacies that sell diabetic supplies. You also can order from an Internet pet pharmacy such as Drs. Foster & Smith[45].

In the US, you can expect to pay $15 to $25 for a box of 100 U100 syringes depending on the retailer and the features of the syringe. Some states and countries[46] require a prescription.


U100 syringes are available in 3 barrel sizes: 1cc (1 ml), 1/2cc (0.5 ml), and 3/10cc (0.3 ml). The size refers to the maximum volume of insulin the syringe will hold; markings can differ with regard to the size of the syringe and the syringe manufacturer[47].

Syringe Sizes

1cc (1 ml) Syringe
Holds maximum: 100 units[48]
Numbered in: 10 unit increments[49]
Smallest line measures: 2 units[50][51][52]
1/2cc (0.5 ml) Syringe
Holds maximum: 50 units[53]
Numbered in: 10 unit increments[54]
Smallest line measures: May vary so count carefully: 1 or 2 units-BD[55][56]
1 unit - Precision,[57]
3/10cc (0.3 ml) Syringe
Holds maximum: 30 units[59]
Numbered in: 5 unit increments[60]
Smallest line measures: 1 unit[61][62][63]
Half-unit scale 3/10cc (0.3 ml) Syringe
Holds maximum: 30 units[64]
Numbered in: 5 unit increments[65]
Smallest line measures: 1/2 unit[66][67]

If for any reason you need to change the size of the 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 1/2cc and 1cc syringes. Some brands of 1/2cc syringes have their smallest non-numbered marks at 2 units[68], others have theirs at 1 unit[69][70] , while 1cc syringes smallest markings are at 2 units.

Because of the small number of insulin units given to cats, most caregivers use the 3/10cc syringe when it is available. The 3/10cc syringe has 1 unit marks. Some manufacturers also have 3/10cc syringes with 1/2 unit marks.[71]


U100 syringes come with a long (12.7mm or 1/2”) or short (8mm or 5/16”) needle. Most syringes with 1/2 unit markings come in the short length, although some manufacturers do put long needles on barrels with 1/2 unit markings.

Some caregivers with long-haired cats prefer the long needle so that they make sure they make it through the fur to the skin. Some feline caregivers prefer the short needle because it minimizes the chance that they will “shoot through” the tent and spill the insulin onto the cat’s fur on the other side. However, some caregivers report difference in insulin absorption with different length needles. BD Diabetes[72] explains that you should consult with your health care professional before using a short needle, and carefully monitor blood glucose when changing to a shorter needle. Some people have found their blood glucose not well-controlled when switching to the shorter needles; this also has been the case with some dogs. Switching back to a longer needle solved the problem. You should consider experimenting with the different length needles.


U100 syringes come in different thicknesses of needle: the gauge (rhymes with "cage"). The higher the gauge number, the thinner the needle[73]. Common gauges range from 28 to 31. Caregivers report that thinner needles make the shot more comfortable for the cat. The 31 gauge syringes are available only with short needles. A 2000 study of children with diabetes ranging in age from 8-21 years compared bleeding, pain/discomfort and insulin leakage using 27-30 gauge needles. Overall, the doctors found no significant differences between any of the needle gauges used[74].

U40 Syringes[]

U40 syringes are intended for use with U40 (40 units per cc) insulin. The "units" therefore appear larger on a U40 syringe, making fine doses easier to measure than on a U100 syringe. But note -- 1/2cc remains 1/2 cc. Comparing two 1/2cc syringes side by side, you will see that the units on the U40 syringe appear larger than that of the U100 syringe. If you were to take the two syringes and fill them with insulin or fluid, both the U100 and the U40 syringe would each hold 1/2cc of it.


U40 syringes are available in 2 barrel sizes: 1cc and 1/2cc. The size refers to the maximum volume of insulin the syringe will hold.

Syringe Sizes

1cc Syringe
Holds maximum: 40 units
Numbered in: 5 unit increments
Smallest line measures: 1 unit
Barrel Markings in: Red: BD, Caninsulin
Black: Vetsulin, Ulti-Care
1/2cc Syringe
Holds maximum: 20 units
Numbered in: 5 unit increments
Smallest line measures: 1 unit
Barrel Markings in: Red: BD, Caninsulin
Black: Vetsulin, Ulti-Care

Some brands of U40 syringes (Caninsulin[75], BD) also have all red barrel markings. Intervet branded Vetsulin syringes and Ulti-Care do not; theirs are in black like those of U100 syringes[76].


U40 insulin syringes are available in standard 1/2" length with a choice of either 28 or 29 gauge needles. The thinnest gauge U40 syringe currently available in the US is 29[77]. BD markets U-40 syringes with 30 gauge needles outside of the US under its MicroFine brand name[78][79].


Though it's not recommended by veterinarians, some caregivers use a U100 syringe with a U40 insulin. That requires “converting” the U40 concentration to a U100 strength[80]. See the conversion tables at the links below[81][82]. If you choose to use the U100 syringes for U40 insulin, a fast way to calculate the right amount of units is to multiply the number of U40 units given by 2.5.

The advantage of doing this conversion is the possibility of greater precision for low-dose animals -- precise dose increments of 0.2 units are possible with half-unit marked U100 syringes (if your insulin is U40). On the other hand, if you find the conversion confusing, it's best not to try -- it can be extremely dangerous to get this math wrong.

Syringe disposal[]

You should dispose of syringes and other "sharps," like lancets, in accordance with your local, state or provincial, or national laws. Consult your trash company, your local or state/provincial health department, or your vet or pharmacist for that information. In some places, sharps have to be disposed of as "medical waste." Some people take them to the vet or pharmacy for such disposal--whether required to by law or not--although that may involve a fee. In other places, there are no specific requirements. You can seal them in a plastic container (such an empty laundry detergent or soda bottle), mark them as sharps, and put them in the regular trash. Some pharmacies also carry sharps containers for about $3-$5 in the US. This page link below[83] has links to additional information under the heading "Needle Disposal."

It may also be possible to fire them into space[84], though this is not recommended :).

Further Reading[]



  1. Parts of an Insulin Syringe-Healthwise
  2. Making the Unit of Insulin-Standards, Clinical Work & Industry-Bulletin of the History of Medicine-2002
  3. Calculateme.com-Milliliter to Cubic Centimeter Converter
  4. BD Diabetes-Insulin Syringes for Cats
  5. BD Diabetes-Insulin Syringes for Dogs
  6. Sarasota Memorial Hospital-Injection Procedures
  7. Vetsulin-Proper Handling of Vetsulin-Reusing Insulin Syringes
  8. Petdiabetes.org-Reusing Syringes
  9. Wikipedia-Precipitation (chemistry)
  10. Vetsulin-Technical Bulletin-Page 3
  11. Insulin Dependent Diabetes-Dr. Ragnar Hanas-Page 21
  12. Injecting Insulin-Transcript of American Diabetes Association Videotape
  13. Washington State University-Diabetes Mellitus
  14. BD Diabetes-BD Inject-Ease
  15. BD Diabetes-Insulin Syringes for Dogs
  16. BD Diabetes-Insulin Syringes for Cats
  17. BD Diabetes-Magni-Guide
  18. PetDiabetes.org-Tips for Comfortable Injections
  19. Injecting Insulin-Transcript of American Diabetes Association Videotape-2003
  20. American Diabetes Association 2002 Position Statement-Insulin Administration
  21. Diabetes Self-Management-Injecting Insulin 101
  22. Syringe Fine Gradations
  23. Syringe Fine Gradations
  24. Bddiabetes.com-Prefilled Syringes
  25. Hocks.com-BD U100 Insulin Syringes
  26. Hocks.com-Monoject U100 Insulin Syringes
  27. Childrenwithdiabetes.com-Insulin Syringe Comparisons
  28. Childrenwithdiabetes.com--Overview of all U100 BD Syringe Types
  29. Wal-Mart-ReliOn Insulin Delivery Devices
  30. ReliOn Insulin Delivery Devices
  31. Childrenwithdiabetes.com-Comparison of ReliOn & BD Syringes
  32. Close-up Comparison-ReliOn 3/10 Short With Half-Unit Markings (Top) & BD UltraFine II Short (bottom)
  33. www.childrenwithdiabetes.com-Precision Sure-Shot Syringes
  34. Terumo Medical-Insulin Syringes-Product Description
  35. Childrenwithdiabetes.com-Abbott Precision U100 Sure-Dose Syringe Comparison
  36. Close-up of a Precision Sure-Dose Syringe
  37. UltiCare-Consumer Ordering Information-Ulti-Care U100 Syringes
  38. Comparison Chart
  39. Hocks.com-U100 Insulin Syringes
  40. Diabetic Promotions Online Shopping
  41. Childrenwithdiabetes.com-Syringes--Prescription Needed or Not?
  42. Prescription Laws From Around the World
  43. Diabetes 123-Prescription Laws From Around the World
  44. Drs. Foster & Smith.com-Insulin Syringes
  45. Drs. Foster & Smith Website
  46. Childrenwithdiabetes.com-Syringes--Prescription Needed or Not?
  47. RxEd.org-Insulin Therapy-Insulin Syringes
  48. Close-up of BD 1cc Syringes-UltraFine-30 Gauge-1/2", UltraFine II Short-31 Gauge-5/16" & MicroFine-28 Gauge-1/2"
  49. Close-up of BD 1cc Syringes-UltraFine-30 Gauge-1/2", UltraFine II Short-31 Gauge-5/16" & MicroFine-28 Gauge-1/2"
  50. Diabetes Mellitus-Washington State University
  51. Close-up of BD 1cc Syringes-UltraFine-30 Gauge-1/2", UltraFine II Short-31 Gauge-5/16" & MicroFine-28 Gauge-1/2"
  52. Terumo Medical (Precision Syringes)Product Description
  53. 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"
  54. 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"
  55. Diabetes Mellitus-Washington State University
  56. 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"
  57. Terumo Medical (Precision Syringes)Product Description
  58. Ulti-Care U100 Syringes-Product Information
  59. 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"
  60. 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"
  61. Diabetes Mellitus-Washington State University
  62. 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"
  63. Terumo Medical (Precision Syringes)Product Description
  64. 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"
  65. 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"
  66. Diabetes Mellitus-Washington State University
  67. 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"
  68. BD 1/2cc Syringes
  69. Terumo Medical (Precision Syringes) Product Description
  70. Ulti-Care U100 Syringes-Product Information
  71. Diabetic Promotions Diabetic Promotions link to 1/2-unit marked syringes by mail
  72. BDdiabetes.com-Using Short Needles
  73. BD Diabetes Insulin Syringe Needles
  74. Pediatric Diabetes 2000-Thinner Needles Do Not Influence Injection Pain, Insulin Leakage or Bleeding in Children & Adolescents With Type 1 Diabetes
  75. Caninsulin Syringes-Italy-Red Barrel Markings Easily Seen in Photo
  76. Ulti-Care U40 Syringes
  77. BD Diabetes-Insulin Syringes for Dogs
  78. BD Diabetes-Germany-1/2 cc (0.5 ml) Syringes with 30 Gauge Needles-Photo
  79. BD Diabetes-Germany- 1cc (1ml) Syringes with 30 Gauge Needles-Photo
  80. Using Caninsulin With U100 Syringes-Page 2
  81. Felinediabetes.com-Using U100 Syringes For U40 Insulins-Conversion Table
  82. Syrnge Conversion Chart U40 to U 100
  83. Childrenwithdiabetes.com-Needle Disposal
  84. Insulin Needle Rocket