I was looking for data on how high an A1c has to be for a person to be very likely to be going into DKA, and came across something entirely different.
This study analyzes the risk of DKA in youth with diabetes (age two to nineteen years) in 2002-2008 taking three or more shots per day, and compares the risk and other characteristics of DKA in those who used Lantus, Levemir, or NPH, had been using the same insulins for at least a year and a half.
To cut to the chase, those using Lantus and Levemir went into DKA way more often; an average of once per 15 years vs an average of once per 28 years for those on NPH. The authors theorize that this is because missing a shot of Lantus or Levemir given once per day was riskier than missing a shot of NPH, which is given twice per day. I'm not entirely convinced. Read the Article
Unfortunately, this study strongly suggests that from the point of view of cost effectiveness, Lantus and Levemir are no good whatsoever. DKA is very expensive. And Lantus and Levemir cost more than NPH. The only advantages shown so far for using Lantus is reduction of hypoglycemia- and hypoglycemia doesn't tend to be very expensive to treat. Levemir given twice per day shows better A1cs than NPH given twice per day, by an average of 0.05 A1c points- statistically significant but not otherwise.
I am going to look for similar studies on adults and rates of DKA in NPH, Lantus, and Levemir users. Maybe I should switch to NPH.