We need to measure 23 U in this syringe. The number 20 is the largest number marked on the syringe that is below the amount we want to measure 23. Because the marks on this syringe are 1 U apart, to measure (23), we must count 3 marks past 20.

Example:

Because regular is faster-acting than Ultralente, we must draw it up into the syringe first. If we look at the syringe closely and think about how a syringe works, we can see that if we draw one kind of insulin up first, once we draw up the second kind of insulin, the first batch will be pushed farther down the syringe, so that the insulin that is drawn up second will be at the top.

So, let's measure the second kind of insulin first so that we can mark it at the top of the syringe, even though in real life, we would draw it up second, after the other insulin.

Because 14 is even, we must measure this dosage using the scale on the syringe to the right.

We need to measure 14 U in this syringe. The number 10 is the largest number marked on the syringe that is below the amount we want to measure 14. Because the marks on this syringe are 2 U apart, to measure 14, we must count 2 marks past 10.

We have already measured the 14 U Ultralente insulin here in blue; now we will measure the 45 U regular insulin in green below it. In order to measure the 45 U regular insulin in green below the 14 U Ultralente insulin in blue, we would have to start from 14 U where the blue stops and count 45 U below that to find the place where the green should stop. Because it is easy to make an error counting this way, and because when we are actually measuring insulin in a syringe we cannot do it that way, we will instead find out where the green should end by marking where the total amount of both insulins together should end.

So, we add 14 to 45 to get 59. This is where the green shading should end.

So now we mark 59 U in green below the blue in the syringe.

Because 59 is odd, we must measure this dosage using the scale on the syringe to the left.

We need to measure 59 U in this syringe. The number 55 is the largest number marked on the syringe that is below the amount we want to measure (59). Because the marks on this syringe are 2 U apart, to measure 59, we must count 2 marks past 55.

Example:

We need to measure 78 U in this syringe. The number 70 is the largest number marked on the syringe that is below the amount we want to measure 78. Because the marks on this syringe are 2 U apart, to measure (78), we must count 4 marks past 70.

Example:

Because Semilente is faster-acting than Ultralente, we must draw it up into the syringe first. If we look at the syringe closely and think about how a syringe works, we can see that if we draw one kind of insulin up first, once we draw up the second kind of insulin, the first batch will be pushed farther down the syringe, so that the insulin that is drawn up second will be at the top.

So, let's measure the second kind of insulin first so that we can mark it at the top of the syringe, even though in real life, we would draw it up second, after the other insulin.

We need to measure 34 U in this syringe. The number 30 is the largest number marked on the syringe that is below the amount we want to measure 34. Because the marks on this syringe are 1 U apart, to measure 34, we must count 4 marks past 30.

We have already measured the 34 U Ultralente insulin here in blue; now we will measure the 13 U Semilente insulin in green below it. In order to measure the 13 U Semilente insulin in green below the 34 U Ultralente insulin in blue, we would have to start from 34 U where the blue stops and count 13 U below that to find the place where the green should stop. Because it is easy to make an error counting this way, and because when we are actually measuring insulin in a syringe we cannot do it that way, we will instead find out where the green should end by marking where the total amount of both insulins together should end.

So, we add 34 to 13 to get 47. This is where the green shading should end.

So now we mark 47 U in green below the blue in the syringe.

Example:

Because Lente is faster-acting than NPH, we must draw it up into the syringe first. If we look at the syringe closely and think about how a syringe works, we can see that if we draw one kind of insulin up first, once we draw up the second kind of insulin, the first batch will be pushed farther down the syringe, so that the insulin that is drawn up second will be at the top.

So, let's measure the second kind of insulin first so that we can mark it at the top of the syringe, even though in real life, we would draw it up second, after the other insulin.

We need to measure 57 U in this syringe. The number 50 is the largest number marked on the syringe that is below the amount we want to measure 57. Because the marks on this syringe are 2 U apart, to measure 57, we must count 3.5 marks past 50.

We have already measured the 57 U NPH insulin here in blue; now we will measure the 22 U Lente insulin in green below it. In order to measure the 22 U Lente insulin in green below the 57 U NPH insulin in blue, we would have to start from 57 U where the blue stops and count 22 U below that to find the place where the green should stop. Because it is easy to make an error counting this way, and because when we are actually measuring insulin in a syringe we cannot do it that way, we will instead find out where the green should end by marking where the total amount of both insulins together should end.

So, we add 57 to 22 to get 79. This is where the green shading should end.

So now we mark 79 U in green below the blue in the syringe.

Example:

Because 37 is odd, we must measure this dosage using the scale on the syringe to the left.

We need to measure 37 U in this syringe. The number 35 is the largest number marked on the syringe that is below the amount we want to measure 37. Because the marks on this syringe are 2 U apart, to measure (37), we must count 1 marks past 35.