Hi Mary,
OK, sit back and take a few deep breaths.
1 - Sumo's numbers so far really haven't been bad. So far you are doing a great job! I can understand you wanting to see if his numbers could go down, and I understand your decision to try 1.5 yesterday.
2 - I don't think the 198 was too drastically low, and I don't think the 501 was drastically high. In case you didn't already know this, the meter has a margin of error of up to 20%. Looking at it optimistically, that 198 could have been as high as a 240, and that 501 could have been as low as a 400. So don't get all freaked out when a number seems to be out of whack. Another thing you can try when you see a number that makes no sense to you is to test again a minute or two later. Sometimes the strip might be wonky, or the blood drop too big or two small. Be concerned if you all of a sudden see a reading of 600 or 60, but otherwise, you're fine. Just collect the data and put it in a spreadsheet so that other people can take a look and tell you what they think.
Chances are, Sumo went low after the 1u into the 198. But I don't think it was "dangerously low". His body has become used to "high" blood glucose levels since he became diabetic. Any time his BG drops a great deal, his body is going to react in a "self-preservation" manner. His liver will think the BG is too low, and it will dump "sugar" into his bloodstream. One of the things that takes place as a cat is getting used to insulin treatments is that it has to readjust to what is "normal" in terms of BG. You are adding insulin into his system that would normally be produced by his pancreas. Insulin is NOT a drug, it is a hormone. What Sumo has is basically a hormone imbalance. Soon, his pancreas will start to "heal", and it will begin producing insulin again. Until that happens, you and your syringe are pretty much doing his pancreas' job.
What you saw today is most likely a "bounce". His liver didn't like the low BG, and it reacted, which pushed his BG back up. That will clear itself in a day or two. Until then, you should stay with 1u and just collect data.
The best thing you can do for the next couple of days is to try to get mid-cycle BG test numbers. Even if you can only get one test in the middle (around 5 or 6 hours after his shot), that will help. You need to determine how low the 1u dose pushes down his BG, so that you will know what to expect if and when you change his dosage.
Another extremely important thing to keep in mind is this : ECID - Every Cat Is Different. Some kitties react to micro dose increases like .1 or .2 units. Other cats don't react as much. I never made an adjustment of less than .25 at a time, in part because I wasn't a member of the board, so I didn't know what was right or wrong, and in part because with the syringes I was using, and my old eyes, I couldn't really adjust in amounts smaller than that. Most times I changed Bob's dose, it was in .5 unit increments, like you did yesterday. Bob was pretty "insulin tolerant" though. He reacted differently than other cats. You still don't know how Sumo is going to react, which is why testing and compiling data is so important.
Keep in mind also - you may not get the same results in the future from something you tried today. His body is going to constantly going through changes on a daily basis. It isn't just the insulin that will affect his BG. His diet, how much and what he eats, his level of activity or stress. All those can influence BG too.
Last thing for now - you shouldn't have to supplement his diet with water. If you see him drinking excessive amounts, that's a cause for concern. But he should get all the water he needs from his wet food. You can also mix water in his food if you think he is looking dehydrated. But cats actually require very little water that isn't provided by their food, assuming they are eating a good low-carb all wet canned food menu.
Carl
