I've been looking into 1 per day myself as this may become a necessity at some point for me. The paper linked by Sienne is terrific ammo for the 2/day home testing approach, and here's some other reading,
A study on healthy cats on the effect of Lantus 1 per day vs 2 per day:
The results were pretty close which gives some promise to the 1/day hopefuls, but the authors state "We predict that better glycaemic control and reduced periods of hyperglycaemia would be achieved in a greater proportion of diabetic cats if glargine is administered twice rather than once daily." They do go on to say "A study involving diabetic cats is required to compare these dosing regimens, and to fully evaluate the potential of glargine for treatment of diabetes mellitus in cats."
Here's one comparing Lantus 1/day vs Lente 2/day in diabetic cats:
It found the two approaches worked similarly. They did Lantus 1/day as this would be an approach clients are more likely to be able to carry out, and do concede that results may have been different if Lantus were given 2/day.
However, when Lantus 2/day is compared to Lente 2/day in diabetic cats in a different study, Lantus won handily (PZI was also compared here):
From the last two you'd expect 2/day Lantus to beat 1/day Lantus, but a controlled direct comparison in diabetic cats would be ideal. 2/day does seems to be by far the preferred method by the people doing the research, and it does seem to yield the best results. 1/day looks feasible if you have no other choice though. Since you are the one giving the shots not your vet, and you're fine with 2/day, the research so far seems to back you.
