Insulin is measured in units, not milliliters. I think you mean 1 unit AM and 0.5 units PM? (I put the 0 in front of the decimal, so it is harder to read it incorrectly.)
Lantus generally works best when dosed the same amount every 12 hours or fairly close to it. When it is injected, it forms small crystals under the skin. this is called the depot. These slowly dissove, releasing the insulin to work. There is always a tiny bit left under the skin when you give the next shot, which results in slightly overlapping effects and an overall lower glucose level.
The Lantus dose is increased based on the nadir, the lowest glucose level between shots. With Lantus, this is often between +5 to +7 hours after the shot. Getting tests during that period help determine how well the insulin is working. You want the nadir to remain safely above 50 mg/dL on a human glucometer. See my signature link Glucometer Notes for more info on how the meters work and what the numbers might mean.