it seems to be common to have periodic problems with lantus, i have come to the conclusion that it is a storage issue with the pharmacies and at home with your own fridge, i have several cartridges that are fine for about a week after removing from the fridge and then start to become ineffective very quickly over 48 hours to the point where i discard the cartridge and open a new one which solves the crisis, there is sometimes a backlash with hypos due to eating less carbs and taking more humolog during the spell where glargine was not performing...i am certain there is a problem with the post manufacturing life span of the glargine, i have had a pack from the hospital pharmacy that was not problematic for two months, then a pack from the local pharmacy that was problematic soon after delivery, i would not suggest that anyone is not storing it correctly, but that the preservative combination used by sonafi is not performing as needed to, while in cold storage for extended periods at the pharmacy...even slight changes in the temperature perhaps to less than the 2-8 degrees C or above could render it prone to problems for the end user..i have a sensitivity to sulfur so humulin I etc is not an option, so i get my insulin from the hospital and discard cartridges after a week, this usually works, but the best idea is to swap if you can and avoid feeling ill and having non regime control issues...hope this helps you feel better.
a general tip is to avoid excessive exercise within 2 hours of injecting your fast acting insulin, as low GI foods are no match for the ability of analog insulins to drain energy from your liver causing long term "low" feelings, take an extra couple of units and rest a couple of hours if possible then have a cup of tea and a biscuit before walking to the shops etc, mild activity at home or at the office does not usually drain you as much and should not cause a constant low and tired feeling...