Insulin treatment regimens in type 1 diabetes

The basal-bolus regimen tries to mimic the normal functioning of the pancreas using two types of insulin [1]. Basal (long-acting) insulin keeps blood glucose stable between meals and overnight, while you give rapid-acting insulin boluses for each meal and for corrections. Basal insulin generally represents 30-50% of the daily requirement [2]. This regimen offers you the greatest flexibility in choosing when and what to eat.

With the basal-bolus regimen you take a minimum of four injections per day, but you achieve the best possible glycemic control [3]. You can make fine adjustments whenever you want. For example, you can skip a meal, eat more or less, make corrections when you need to. It is the gold standard regimen for administering insulin injections in type 1 diabetes because it comes closest to normal pancreatic function, as the figure below shows [1].

Most people with type 1 diabetes take between four and eight injections per day [3]. The minimum for the basal-bolus regimen is four. You take one long-acting insulin injection and one rapid-acting insulin injection for each of the three main meals [2]. In reality, most patients take more than six injections by adding corrections for hyperglycemia or boluses for snacks.

There is no "too many" injections if they improve your control. Some highly motivated people take ten injections daily for the best possible glycemic control. Insulin pumps replace multiple injections with hundreds of micro-doses per day, although the infusion set still has to be changed every few days, which also involves a needle prick [4]. The important thing is to take enough injections to keep your blood glucose on target, not to minimize their number.

The intensive physiological regimen means actively and frequently adjusting your insulin doses according to blood glucose, carbohydrates, physical activity, and other factors [5]. It includes a minimum of four injections per day (or a pump), measuring blood glucose at least four times per day, and precise dose calculation. You don't follow fixed doses, but adapt each dose to the current situation using insulin-to-carbohydrate ratios (how many grams of carbohydrate one unit of insulin covers) and correction factors (how much one unit of insulin lowers blood glucose), which differ across various time intervals [3].

The intensive physiological regimen requires solid diabetes education, but offers the best control and the greatest freedom. The DCCT study (the landmark trial that compared intensive with conventional treatment in type 1 diabetes) demonstrated that it significantly reduces long-term complications [5]. It requires dedication and continuous learning. It is the only regimen currently recommended for type 1 diabetes [2].

It is not a suitable regimen today. The two-injection regimen (mixed insulin in the morning and evening) is outdated and inadequate for most people with type 1 diabetes [5]. It provides poor glycemic control, requires meals and snacks at fixed times, and does not allow flexibility [2]. It may be temporarily acceptable only in special situations, such as elderly people with severe cognitive problems.

With only two injections you cannot correct hyperglycemia, cannot adapt doses to meal content, and you risk frequent hypoglycemia due to the action peaks of NPH (neutral protamine Hagedorn) insulin (an intermediate-acting human insulin) [1]. HbA1c will probably be above 8% (64 mmol/mol) and the risk of complications consequently increases significantly [5]. If your doctor proposes this regimen for type 1 diabetes, ask what the reason for this choice is and how long the regimen is meant to last; if anything remains unclear, you can also seek a second opinion from another diabetologist.

If you forget your mealtime rapid-acting insulin and remember within the first hour, the full dose can be taken immediately, according to the protocol agreed with the medical team [6]. Between one and three hours, check your blood glucose and be cautious with additional doses to avoid insulin overlap ("stacking") [2]. After three hours from the meal, don't take the meal dose anymore, only a correction based on your current blood glucose. Check your blood glucose two hours after taking the correction and monitor carefully for the next 12 hours. Hypoglycemia means a blood glucose below 70 mg/dL (3.9 mmol/L): you take 15 g of fast-acting carbohydrate and recheck after 15 minutes. The complete steps are on the pages about what hypoglycemia is and about how to treat it.

For missed basal insulin, what you do depends on the insulin and on how much time has passed: a missed dose of insulin glargine (or of another basal insulin lasting about 24 hours) is taken if less than about 12 hours have passed since your usual time, otherwise it is skipped and resumed the next day, following the personal protocol agreed with your doctor [6]. If you took the dose late, gradually shift the administration time in the following days to return to your usual time. For insulin degludec (a basal insulin with a very long duration of action), if you have forgotten your evening dose, you can take it in the morning, and return to your usual evening time only once your doctor's minimum interval between two doses has passed; two doses given too close together increase the risk of hypoglycemia [1]. Monitor your blood glucose carefully and make corrections with rapid-acting insulin if needed.

The regimen and the titration steps are decided together with your medical team. Dose adjustment is done gradually, changing the dose very little and waiting three days to see the effect [7]. For basal insulin, if blood glucose rises or falls too much overnight, the adjustment is usually of 1-2 units, according to the plan agreed with the medical team [2]. For meal boluses, if blood glucose two hours after a meal is consistently too high or too low, modify the insulin-to-carbohydrate ratio.

Keep a detailed log with blood glucose readings, doses, carbohydrates, and activities to identify patterns [8]. The general rule is that if you see the same pattern for several days in a row, make a small adjustment. Don't make big changes. Small and repeated adjustments are better [7]. Learn to distinguish between an atypical day and a real trend that truly requires an adjustment.

Children use the same basal-bolus regimens as adults, but with age-specific particularities [3]. Doses are much smaller and require frequent adjustments. Sometimes insulin dilutions are used for very small doses [9]. The insulin pump is ideal for children because of the small doses needed, but also for the precision and flexibility it offers [4].

Parents must be taught to manage the tendency toward high glycemic variability [9]. Children's physical activity is sometimes unpredictable, their meals are irregular, and they quite often catch the usual childhood illnesses. Adolescents need higher doses because of the insulin resistance associated with puberty, sometimes reaching 1.2-1.5 units/kg/day [3]. The regimen must allow the child progressive autonomy, gradually learning to manage their diabetes on their own.

The insulin pump offers clear advantages: more precise dosing, programmable basal rates for different times of day, extended boluses for complex meals, and the elimination of multiple injections [4]. Studies show a similar or slightly better HbA1c with the standard pump, but fewer severe hypoglycemic episodes and less glycemic variability [10]. Quality of life is usually better with the pump. Nevertheless, the standard pump does not guarantee better control [11].

Some people achieve excellent control with insulin pens and prefer not to be "connected" permanently to a device. The pump is more expensive and requires technical training. The best option is the one you use correctly and consistently. The exception is the pump capable of closed-loop operation (with automatic insulin adjustment based on sensor readings), which usually offers better control than external injections, when it is available and suited to your situation [4].

Not instead of insulin. In type 1 diabetes the pancreas no longer makes insulin, and no medicine in this class replaces that. What has been studied is adding it to insulin, in patients with type 1 diabetes and excess weight. Pooled results show a weight loss of about 4 kg and a small drop in HbA1c, of roughly 0.25 percentage points, while the insulin requirement falls by almost 10 units a day [12].

The price shows up in the same data: hypoglycemia was more frequent, and nausea and vomiting appeared significantly more often [12]. The class is not approved for type 1 diabetes, and the evidence comes from small studies or from everyday practice. One large phase 3 trial is under way [13]. Until its results, the use remains an off-label decision, meaning it is not covered by the product label. If it is started, insulin doses are reduced from the outset, with ketone bodies watched closely.