Can Blood Glucose Be Controlled Using Only Human Regular Insulin (Actrapid)?
No, blood glucose cannot be adequately controlled using only human regular insulin (Actrapid) without basal insulin or other therapies in most patients with diabetes. Regular insulin alone addresses only meal-related glucose excursions and fails to suppress hepatic glucose production between meals and overnight, leading to uncontrolled fasting hyperglycemia and dangerous glucose fluctuations.1
Why Regular Insulin Alone Is Insufficient
Lack of Basal Coverage
- Basal insulin is essential to restrain hepatic glucose production and limit hyperglycemia overnight and between meals; regular insulin (Actrapid) provides only short-term coverage (onset 30 minutes, peak 2–4 hours, duration 6–8 hours) and cannot fulfill this role.1
- Without basal insulin, patients experience persistent fasting hyperglycemia because hepatic glucose output remains unsuppressed during the 12–16 hour intervals between regular insulin doses.1
- The progressive nature of type 2 diabetes means that many patients eventually require and benefit from insulin therapy, but this must include both basal and prandial components to mimic physiologic insulin secretion.1
Guideline Condemnation of Prandial-Only Regimens
- All major diabetes guidelines explicitly condemn the use of prandial insulin (including regular insulin) as monotherapy without basal insulin, as it reacts to hyperglycemia rather than preventing it and causes dangerous glucose fluctuations.2
- Sliding-scale or correction-only insulin regimens—which rely solely on short-acting insulin like Actrapid—achieve adequate glycemic control in only ≈38% of patients, compared with ≈68% when a scheduled basal-bolus regimen is used.2
The Correct Approach: Basal-Bolus Therapy
Basal Insulin as the Foundation
- Basal insulin (NPH, glargine, detemir, or degludec) is the preferred initial insulin regimen in patients with type 2 diabetes, providing continuous background coverage to suppress hepatic glucose production.1
- Starting doses can be estimated at 0.1–0.2 units/kg/day (or 10 units once daily), with individualized titration over days to weeks as needed.1
- Long-acting basal analogs (glargine, detemir) have been demonstrated to reduce the risk of symptomatic and nocturnal hypoglycemia compared with NPH insulin, though these advantages are modest.1
Adding Prandial Insulin When Needed
- Short- and rapid-acting insulin formulations (including regular human insulin like Actrapid) are used to intensify basal insulin therapy in patients not meeting glycemic targets, not as standalone treatment.1
- Prandial insulin should be added when basal insulin has been optimized (fasting glucose 80–130 mg/dL) but HbA1c remains above target after 3–6 months, or when basal insulin dose approaches 0.5–1.0 units/kg/day without achieving HbA1c goals.2
- Start with 4 units of regular insulin before the largest meal (or 10% of the basal dose), administered 30 minutes before eating, and titrate by 1–2 units twice weekly based on 2-hour postprandial glucose readings.3
Practical Considerations for Regular Insulin (Actrapid)
Timing and Administration
- Regular human insulin must be injected 30–45 minutes before meals to achieve optimal postprandial glucose control, which is less convenient than rapid-acting analogs that can be given 0–15 minutes before eating.4, 5
- This longer pre-meal interval increases the risk of late postprandial hypoglycemia if the meal is delayed or smaller than anticipated.5
Efficacy Compared to Rapid-Acting Analogs
- Regular human insulin provides similar HbA1c control compared to rapid-acting analogs (lispro, aspart, glulisine) in type 2 diabetes, with minimal differences in glycemic efficacy.3, 6
- However, rapid-acting analogs have a modestly lower risk for hypoglycemia (especially nocturnal and severe hypoglycemia) and better postprandial glucose control compared to regular human insulin.1, 6, 7
- In type 1 diabetes, immediate pre-meal administration of rapid-acting analogs results in improved postprandial glucose control compared to regular insulin injected immediately before the meal, but shows similar control when regular insulin is injected 30 minutes before the meal.8
Cost and Accessibility
- Regular human insulin (including Actrapid) is significantly less expensive than rapid-acting analogs, making it a practical choice for patients with financial constraints or limited health literacy.3
- The way insulin is administered has a greater impact on outcomes than differences among insulin formulations, so proper patient education on timing, hypoglycemia recognition, and consistent meal timing is critically important regardless of insulin type.3
Special Populations and Alternative Strategies
Type 1 Diabetes
- Insulin is the primary treatment in all patients with type 1 diabetes, and patients typically require initiation with multiple daily injections at diagnosis: short-acting or rapid-acting insulin given 0–15 minutes before meals together with one or more daily separate injections of intermediate or long-acting insulin.4
- Two or three premixed insulin injections per day may be used, but basal-bolus regimens are preferred to allow independent titration of basal and prandial components.4
Type 2 Diabetes
- Indications for exogenous insulin therapy in type 2 diabetes include acute illness or surgery, pregnancy, glucose toxicity, contraindications to or failure to achieve goals with oral antidiabetic medications, and a need for flexible therapy.4
- Insulin is considered alone or in combination with oral agents when HbA1c is ≥7.5% (≥58 mmol/mol), and is essential for treatment in those with HbA1c ≥10% (≥86 mmol/mol) when diet, physical activity, and other antihyperglycemic agents have been optimally used.4
- The preferred method of insulin initiation is to begin by adding a long-acting (basal) insulin or once-daily premixed insulin, alone or in combination with GLP-1 receptor agonist or other oral antidiabetic drugs.4
Combination with Metformin
- Metformin combined with insulin is associated with decreased weight gain, lower insulin dose, and less hypoglycemia when compared with insulin alone.4
- Oral medications should not be abruptly discontinued when starting insulin therapy because of the risk of rebound hyperglycemia.4
Critical Pitfalls to Avoid
- Never use regular insulin (Actrapid) as monotherapy without basal insulin coverage; this reactive approach is condemned by all major diabetes guidelines and causes dangerous glucose fluctuations.2
- Do not delay insulin initiation in patients not achieving glycemic goals with oral medications alone, as prolonged hyperglycemia exposure increases complication risk.2
- Do not rely solely on correction doses without adjusting scheduled basal and prandial insulin; correction insulin must supplement, not replace, a scheduled basal-bolus regimen.2
- Avoid using rapid-acting or regular insulin at bedtime as a sole correction dose, as this markedly raises the risk of nocturnal hypoglycemia.2
Expected Clinical Outcomes
- With a properly implemented basal-bolus regimen (basal insulin + prandial regular insulin), approximately 68% of patients achieve mean glucose <140 mg/dL, compared with only 38% using prandial insulin alone.2
- HbA1c reductions of 2–3% are achievable within 3–6 months with intensive insulin titration when both basal and prandial components are optimized.2
- Properly executed basal-bolus regimens do not increase overall hypoglycemia incidence compared with inadequate prandial-only approaches when correctly applied.2