I think that your GP has started you on low doses for sound safety reasons. It might take some time to titrate it upwards to the appropriate dose but at the beginning he has absolutely no idea about how insulin sensitive you are.
(drugs aimed at people who are often insulin resistant don't seem to have worked well so perhaps you could actually be more insulin deficient than resistant as suggested by previous posters).
He has to make sure that he doesn't give too much too quickly with a big hypo as a result. He is probably using a local guideline for insulin initiation and these do differ from area to area.
One guideline I read suggested starting at 60% of average levels and titrating upwards.
An average is often said to be 0.5u of insulin per kg but this is only a rough ball park figure, many take much more or much less
http://library.nhsggc.org.uk/mediaAsset ... 010-01.pdf
When you adjust this type of insulin normal practice is to do it gradually with at least 48 hours between each adjustment . You also don't do it on the basis of one reading.
It's only a week in so it will take time to get better control but obviously discuss it with your doc tomorrow.
It's worth bearing in mind that mixed insulin's contain 2 types of insulin. One covers the glucose released from the liver during the day and the other covers the carb intake. You can't adjust the proportions but can work well with a regular lifestyle.
They work best with
consistent carbohydrate amounts
both in time of day and amount.
If you eat 20g carb for dinner at 6pm one day and 50g carb at 8pm the next it wont' work well at all.
eg: if the amount you take each day will cover 50g of carbs you would be hypo if you only ate 20g carbs.
If you vary the time too much the background element of the insulin won't be spread out over the 24hours.
Because these insulins have peaks and troughs some people also have to take snacks between some meals or at bedtime .... but that bit comes later when you discover the patterns that apply to you personally. Record keeping is really important to work these out.