Hi
@Bassiette, Sorry to hear of your sleep troubles.
As you might imagine the whole subject of thirst and making of urine involves a lot of body processes from the brain, hormones, digestion of food, uptake of water through to the 'plumbing' - kidneys, bladder etc.
Just some thoughts, i agree with
@JMK1954 , that our brain can habitually follow an earlier behaviour pattern.
But also, if you look up rxlist.com Lantus - Side-effects in Detail you can see that nightmares and sleep disturbance figure, and also fluid retention, swelling of legs, hands sometimes face.
A thought is whether Lantus is causing you to retain fluid ( in the tissues under the skin, say,)and believe it or not it ir not it happens that our kidneys, those filters of the blood , actually work more efficiently, produce more urine when we are laying diwn flat ( see
https://www.bladder and bowel.org-
nocturia.
So even if you were not drinking much fluid before bedtime, the accumulated fluid from during the day might still he enough for the kidneys to cause sufficient bladder-filling to disturb your sleep.
Maybe, if you have access to accurate scales you could try weighing yourself morning and night under similar conditions e.g. same amount of clothing, before eating food, or drinking fluid and may be after emptying one' s bladder etc rather than before.
With this info and asuming your life is being adversely affected by nighttime disturbance you could consult your doctor, see what he/she makes of it and go from there.
I am not suggesting that you have to change from Lantus necessariky but if no other cause is apparent that might be a consideration.
Good Luck !