Hello Diabolus X,
(This is a copy-and-paste of a reply I have made on several other threads. Hopefully it's helpful for you).
Lantus Insulin is slightly acidic; when the acidic solution hits healthy fatty tissue it forms tiny crystals. These crystals then dissolve at a uniform rate, giving a steady release of the Insulin over approximately 20 - 24 hours. The injection site is really important for Lantus. If you hit a non-fatty area (blood vessel, or muscle, or
possibly an area damaged by previous injections) then these crystals do not form correctly. This can mean large amounts of the Insulin active immediately and acting more like a Rapid Insulin.
I had problems with overnight lows. After discovering the above information, I started to take more care with my Lantus injections, and for me the overnight lows stopped immediately. I now scrupulously avoid 1 area of belly tissue that had been damaged by Lantus injections with larger disposable needles over many previous years. And I now make sure to rotate my Lantus injection sites, ensuring to take a good pinch of healthy tissue. Basic stuff that I should have been doing anyway, I guess.
After this small change, the overnight lows stopped immediately and I was able to reduce my Lantus dose from 18 to 14, without changing anything else in my routine.
http://www.lantus.com/starting/how-to-use/choosing-site.aspx
The information available for Lantus does give all the right advice about how to inject. But it does not give any information regarding WHY it is important to get it right. How the Insulin is designed to work is not explained, and I think this is very unhelpful. Obviously there are serious effects if it acts more like a Rapid Insulin.
Regards,
Antony