17 of Lantus isn't alot of Insulin ,I am insulin dependent and take double that .
Interesting thing about Long acting insulin ,you realy can't "hurt" yourself with it , as long acting won't dramatically drop your BG the way short acting can drop your sugar fast without eating .

My suggestion to protect this person would be talk to the doctor( Endocrinologist) about a CGM Continuous Glucose Monitor ,its covered by most insurance including Medicare Medicade , it will give a reading every five minutes ,so better control of BG it can also give your doctor access to sugars Via web portal ,and assuming you have (i cant believe I am saying this ) basic technology like an IPad IPod or IPhone you can pair it with your device via Bluetooth, which is paired with an Amazon Echo or Google home , you can then have your assistant announce your BG and tell you if your trending up or down and do alarms and all kinds of neat technology stuff . And as a diabetic I can absolutely say not having to stab your finger to test your BG is the best thing since sliced (wheat) bread. And the sensor that attaches to your body is only changed every 10 days ,so 3 times a month is bonus time ,( here i go again,LOL) that you can use to plan your meals, I love to eat ,good food, and therefore devote alot of time , to cooking healthy flavorful ( throw moderation to the wind and pig out !,meals.,that don't send my sugar into the stratosphere if I do ).

On a side note about our barbaric past treatments from the realm of Psychiatry, back in the day When men where men and patients where afraid ( only half kidding ) a treatment for Schizophrenia and bipolar was both ECT and insulin shock therapy ,imagine that ? , ECT is still around ,insulin shock therapy bad idea ,"bad medicine" ,more patients probably accidentally died than got helped .

I am a walking ,talking, functioning not feeling "right" but cant put my finger on whats wrong ,non low BG feeling person , not feeling "right" translated to my BG was 22! Many diabetics will be in a hypoglycemic coma at that , me I wander in and talk to the E.D doc ,sure it maybe less than spectacular brain function ,but it scares the doctors that your not presenting as a medical emergency in a coma .

Peace