Even when you can't dilute insulin, it's possible, with a lot of patience and a good magnifier, to dose insulin in fine gradations. Since a small dog or cat may weigh 1/10 what an average human does, it shouldn't be surprising that a 1 unit change in a human is sometimes like a 1/10 unit change in a small animal.
With U40 insulin[]
With U40 insulin, you can dose insulin to a precision of 0.2 units by using a U100, half-unit marked syringe, and converting.
With U100 insulin[]
But with U100 insulin, all you can do is use patience and good eyesight to "eyeball" fine doses. Consistency is more important than accuracy -- if you can give the same amount reliably tomorrow, you have succeeded.
It is indispensable to use half-unit marked U100 syringes. The insulin syringes with half-unit markings are available here:[1][2]
Pictures method[]
The Fine Doses Picture guide shows one numbering method.
Note that some syringe makers have inconsistent zero line adjustments with significant variation. See this discussion: http://www.felinediabetes.com/phorum5/read.php?22,1462377
Fat/thin/touching method[]
Another works like this:
- 0.5U = on the 0.5U line
- 0.4U = thin 0.5U - touching the edge of the line
- 0.3U = thin 0.5U - no longer touching the edge - some daylight between
- 0.2U = fat 0.0U - not touching the zero line
- 0.1U = fat 0.0U - touching the edge of the line
- 0.0U = On the zero line
Droplet method[]
Stefanie & Toonces of the FDMB use a "droplet" method.[3][4]