Part of Dr.Katharine Morrison’s “How To” series as posted in this forum post (requires registration).
The best way to find out the best basal for you is usually to look at the 3am bs. Do this several times but don’t look at the averages, look at the lowest number you are getting. The aim is to give you normal night sugars but not hypoglycaemia.
If your lowest bs at 3am is 5.0 your basal is right for you.
If your lowest am bs is less than 5.0 you are having too much basal.
If your lowest 3am is less than 5.0 you are also having too much basal.
If your average am bs over at least 3 but preferably 10-14 is higher than 5.0 with good 3am bs you are having the dawn phenomenon. If you gave a higher basal to get this down you would be giving yourself a high risk of night time lows.
If your lowest 3am is higher than 5.0 you can try a slight increase in basal.
Make changes in insulin doseage in the smallest increments your pen allows. Vial and syringes do give more flexibility. Diluted insulin can also make incremental changes more precise and is particularly helpful for young children and babies who are on low amounts of insulin.
When you have made a change in basal insulin sit it out for about 3 days before you adjust again. This is the time it can take for this to stabilise.