When you skip a shot, the glucose goes up by the next shot time. That should make sense.
The body is in constant flux. On the average, a given dose will have a given effect in a cat until something changes. When a change occurs, the glucose level may shift up or down or do nothing at all. That's why we test. We cannot always predict what other factors have changed (ex food batches, a hairball, illness, etc) and want to know the numbers before shooting to ensure safety (at or above 50 mg/dL) and effectiveness (nadir below 150 mg/dL).
You have been using the Lantus long enough that you may begin to lower the "no shoot" number 10-20 mg/dL a week down until you reach 150 mg/dL, as you become more comfortable with lower numbers. Once you are shooting at 150 mg/dL, you'll find more guidance on how to shoot low to stay low in the Lantus Tight Regulation forum. Some of those folks shoot at much lower numbers because they can monitor and have collected data to show it is safe for their respective cats.
If giving 1 unit results in a non-shootable number, then drop to 0.75 units. You may have to eyeball this. Barring a test below 50 mg/dL, keep the dose the same for a minimum of 3 days, then use the nadir on the 4th day to see how effective the dose is.
