Type 1 diabetes is treated with insulin. Depending on the age of the patient and other factors, tight control of the blood sugar might be recommended to lessen the risk of developing complications of the diabetes.
Type 1 diabetes usually begins in the teenage years, but may have an earlier or later onset, with the hallmark being the presence of diabetic ketoacidosis either at presentation or in the absence of insulin therapy.
Type 1 diabetics require insulin therapy to maintain normal glucose and lipid metabolism. This is non-negotiable, and there are really no other alternatives in the management of this condition, which can be life-threatening.
1. Human insulin vs. insulin analogues
Insulin was previously harvested from animal pancreases, but this form of insulin included impurities, which lead to allergies in some people.
Current insulin preparations are manufactured using recombinant DNA technology and can be broadly classified into two categories:
- Human insulin, which is identical to human insulin in structure for example Actrapid, Humulin N, Insuman, Humulin 30/70, Actraphane and Insuman 30/70
- Human insulin analogues, in which one or two amino acids of human insulin are changed
Examples are Apidra, Humalog, Novorapid, Lantus, Levemir, Novomix 30 and Humalog Mix 25.
Duration of action
The next factor in classifying insulin is considering the duration of action:
Rapid-acting insulins are the insulin analogues such as Apidra, Humalog and Novorapid that have an onset of action of approximately 15 minutes. They peak at approximately 30 to 90 minutes and have a duration of action of less than 3 hours.
The rapid-acting insulins are used 5 to 10 minutes prior to or at mealtimes and typically cover the post-meal blood-glucose surges, provided that the dose is correct.
The regular short-acting insulins are human insulins that take longer to peak and have a longer duration of action compared with the analogue insulins.
Regular insulin has an onset of action of approximately 30 to 60 minutes, a peak at between 1 and 2 hours, and a duration of action of more or less 3 to 5 hours.
Examples of regular insulins are Insuman, Actrapid and Humulin R.
The regular insulin is typically taken 30 minutes prior to a meal. The dose of these short-acting insulins will be determined by the blood glucose reading before the meal and by the amount and perhaps type of carbohydrate in the intended meal.
The intermediate-acting insulins (Humulin N, Protophane) are regular insulins that, when attached to zinc or NPH (Neutral Protamine Hagedorn), have an altered onset, peak and duration.
These insulins are usually given subcutaneously every 12 hours. They have an onset of action of approximately 2–3 hours, they peak at more or less 8–12 hours, and they have a duration of action of about 16 hours.
Note that these are approximate figures only and may vary depending on many factors. The long-acting insulin analogues are Lantus and Levemir. Lantus, which has a duration of action of about 24 hours without a peak level, is taken once daily.
Levemir has a more contentious duration of action that is dose-dependent. This form of insulin is taken once or twice a day, depending on the degree of control needed.
Then there are the fixed-dose combinations of rapid or short-acting insulin and intermediate-acting insulin in fixed-dose combinations of 25%:75%, 30%:70% or 50%:50%.
The first number of the ratio applies to the percentage of rapid- or short-acting insulin in the mixture.
Different insulin regimens
In healthy people, insulin is secreted at a constant, low level over 24 hours. This prevents glucose release by the liver, which may occur via the process of gluconeogenesis (when glucose is produced from non-carbohydrate sources such as amino acids) and glycogenolysis (when the carbohydrate, glycogen, is broken down into glucose).
Insulin secretion is increased during/after food when digestion of food leads to an increase in blood glucose. The insulin helps to keep the blood-glucose levels within a normal range.
In type 1 diabetics, the aim is to mimic normal insulin secretion, which is best done by the so-called "basal bolus regimen". This means that a long-acting insulin such as Lantus or Levemir is given once a day, at the same time (for example at 21:00).
This is to provide a 24-hour basal insulin supply. The aim is to keep the fasting blood glucose between 4 and 7mmol/l. Rapid-acting or short-acting insulin is then taken before meals to cover meal-time surges in glucose.
This usually involves giving insulin up to three injections during the day. So, the basal bolus regimen usually involves up to four injections per day. It gives the diabetic some flexibility, better blood-glucose control and fewer hypoglycaemic episodes (when there's too little glucose in the bloodstream), especially if the insulin analogues are used.
Another regimen is to use a twice-daily premixed insulin at breakfast and supper. However, in some diabetics a third dose may be needed at lunchtime.
Doses are best worked out by the prescribing doctor and sometimes by a diabetic nurse. Note that every diabetic is prescribed their own appropriate dose. Don't compare your dose to that of another diabetic, as their circumstances may be very different to yours.
Treating type 2 diabetes
Reviewed by Dr Hilton Kaplan, MB BCH (Rand), FCP(SA), MMed(UCT), Specialist Endocrinologist and Physician (March 2016)