How to Convert U-100 Insulin in Units to Milliliters

How to Convert U-100 Insulin in Units to Milliliters

Insulin syringes and insulin bottle on white background.Insulin syringes and insulin bottle on white background.
Insulin syringes and insulin bottle on white background.Insulin syringes and insulin bottle on white background.

Insulin is an injectable medication used to treat diabetes mellitus in dogs, cats, and other animal species. It is available in a variety of types and strengths. There are also different sizes of insulin syringes that are made to go with the varying types of insulin.

KEY POINT: There are different types of insulin syringes. It is critical to match the correct syringe with the accompanying type of insulin to administer an accurate dose.

The best way to ensure that you give the correct amount of insulin to your cat or dog is to understand the strength and type of insulin and use the syringe that is made to go with the applicable insulin.

They may be instances where you are unable to match your syringe and insulin type, due to lack of availability or an emergency. This article is designed to help pet owners accurately convert insulin units to ml.

Understanding Insulin Strengths

Common strengths of insulin used in dogs and cats are referred to as U-100 or U-40. “U” stands for unit. The numbers 40 or 100 refer to how much insulin (the number of units) is in a set volume of fluid – which, in this case, is one milliliter (1 ml) [referred to as units per ml]. For example, U-100 insulin has 100 units per milliliter and U-40 has 40 units per milliliter.

KEY POINT: Some insulin syringes have more than 2 ½ times the units of insulin per ml.

  • U-100 syringes hold 100 units per milliliter
  • U-40 syringes hold 40 units per milliliter

It is possible to use a 1 ml (commonly referred to as a TB syringe) for insulin.

Examples of Insulins:

Novolin® N is an example of a U-100 insulin.
Notice that the label on the bottle and box indicates that this insulin is 100 units/ml.


  • Examples of U-100 insulin are Humulin R U-100, Lantus®, Humulin N, Novolin® N, Relion®, and Humalog® U-100.
  • Examples of U-40 insulin are Vetsulin® and ProZinc®.

So, U-100 insulin is more concentrated. There is essentially 2 ½ times more insulin in a milliliter than there is in U-40 insulin.

Lantus® SoloStar® insulin glargine injection is another example of a U-100 insulin.
It is critical to use a U-100 insulin syringe for accurate dosing.


Note: Always look at the bottle to double check the strength of your insulin. There are new insulins on the market that are U-300 and U-500, which are used in humans, but are not commonly used in dogs and cats.

Understanding Insulin Syringes

To go with the different types of insulin, there are different syringes, including U-40 syringes and U-100 syringes. It is important to use the right syringe with the right insulin to achieve the correct dosage. Your veterinarian should prescribe syringes and insulin that match. The bottle and the syringes should each indicate if they are U-100 or U-40. Again, make sure they match.

It is possible to “convert” and mix and match the insulin syringes. It is generally not recommended because it can lead to deadly mistakes.

  • One unit of U-40 insulin is 0.025 ml in a regular syringe.
  • One unit of U-100 insulin is 0.01 ml in a regular syringe.
Package of a U-100 insulin syringe.
Observe that the package clearly shows that it is a U-100 syringe. This particular syringe indicates that it will dose up to 50 insulin units. There are other syringes available that will dose 30 or 100 units. If you are giving a small dose of insulin, the 0.3 ml syringe is a better choice, because it allows you to see the numbers more clearly, which will help you pull up the most accurate dose of insulin.


Using non-matching equipment is not ideal and should only be done after consulting with your veterinarian and confirming the “dose” and what equipment is being used (it is ideal to have someone double check you and your math – this is no place for experiments or errors).

To convert U-40 insulin to a U-100 syringe – please read this article: How to Convert U-100 and U-40 Insulin and Syringes.

Communicating with Your Veterinarian

IMPORTANT: Make sure that you communicate with your veterinarian prior to any changes. It is important that he or she knows exactly how much insulin your dog or cat is getting. Because of the “conversion,” you need to be sure to tell them the type of insulin and strength (U-100 or U-40), the type of insulin syringe (U-40 or U-100), and the amount, so that they can determine the actual amount of insulin your pet is getting.

A U-100 insulin syringe (orange cap on top) and a 1 ml regular syringe (bottom).

How to Convert Insulin Units to Milliliters (ml) Using U-100 Insulin

Although matching insulin and syringes is ideal, on occasion, an owner will find themselves with insulin and syringes that don’t match. Below is a conversion chart to help those who need to convert units of insulin to ml. You will find the amount you need to use with the conversion next to it.

To administer this amount
of U-100 insulin
Draw to this level
in a 1 ml syringe
1 unit 0.01mls
2 units 0.02 mls
3 units 0.03 mls
4 units 0.04 mls
5 units 0.05 mls
6 units 0.06 mls
7 units 0.07 mls
8 units 0.08 mls
9 units 0.09 mls
10 units 0.1 mls
11 units 0.11mls
12 units 0.12 mls
13 units 0.13 mls
14 units 0.14 mls
15 units 0.15 mls
16 units 0.16 mls
17 units 0.17 mls
18 units 0.18 mls
19 units 0.19 mls
20 units 0.20 mls
21 units 0.21 mls
22 units 0.22 mls
23 units 0.23 mls
23 units 0.24 mls
25 units 0.25 mls
26 units 0.26 mls
27 units 0.27 mls
28 units 0.28 mls
29 units 0.29 mls
30 units 0.30 mls
31 units 0.31 mls
32 units 0.32 mls
33 units 0.33 mls
34 units 0.34 mls
35 units 0.35 mls
36 units 0.36 mls
37 units 0.37 mls
38 units 0.38 mls
39 units 0.39 mls
40 units 0.40 mls
41 units 0.41 mls
42 units 0.42 mls
43 units 0.43 mls
44 units 0.44 mls
45 units 0.45 mls
46 units 0.46 mls
47 units 0.47 mls
48 units 0.48 mls
49 units 0.49 mls
50 units 0.50 mls

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