Thanks for that.sounds very complicated. Do you mean I inject all the insulin in one go or as I am doing twice daily.
People need insulin to counteract the sugar in food they've eaten but also to burn sugar provided by the liver when we're fasting (eg at night your stomach is empty but your body is still using energy).
Many of us are on basal/bolus regimes. Basal insulin is long acting and carries us through the day and night when we're not eating so if you get the dose right your blood sugar is where you want it to be in the morning, Most people have one basal injection (either first thing in the morning or last thing at night) though some people have two. Bolus insulin is short acting, just a few hours, so it deals with any food you eat, and you can adjust it both to cope with different amounts of food, different times of food (eg having a midnight snack or missing out a meal) and you can add in extra if your blood sugar is too high and you want to reduce it. So this provides a lot more flexibility than your current regime but typically will have 4 injections per day (one basal and a bolus before each meal). And you'll also be MUCH better off if you learn to count carbs properly and calculate the amount of insulin you need. (The diabetic clinic should teach you this.)
How can I reduce one without reducing the other.
You can't on your current system.
Your current system is fine if it works for you but becomes difficult if you want to change carbohydrate amounts, times of meals or correct for high sugars. Because you're injecting a mixture of long and short acting insulin, if you increase your dose to cope with high blood sugar or extra food you risk going low in 6 hours time when your your increased basal is hitting you but your food has run out.
Really you need to talk to your diabetic team about your issues and get specific advice about how to correct your doses. Good luck.