Why Sliding Scale is Added to 70/30 Insulin in Hospitalized Patients
Sliding scale should NOT be added to 70/30 insulin in hospitalized patients—this combination is explicitly discouraged due to unacceptably high rates of hypoglycemia, and 70/30 premixed insulin itself is not recommended for inpatient use. 1
The Evidence Against 70/30 Insulin in Hospitals
Premixed 70/30 insulin (NPH/Regular) has been associated with unacceptably high rates of iatrogenic hypoglycemia and is not recommended in the hospital setting. 1 A key study comparing 70/30 premixed insulin versus basal-bolus therapy was stopped early after interim analysis revealed that 64% of patients in the premixed group experienced hypoglycemia compared to only 24% in the basal-bolus group, despite no difference in glycemic control. 1
The 2019 American Diabetes Association guidelines explicitly state that while premixed insulin formulations have evidence for outpatient use, a recent inpatient study showed comparable glycemic control but significantly increased hypoglycemia with 70/30 NPH/regular insulin versus basal-bolus therapy, and therefore premixed insulin regimens are not routinely recommended for in-hospital use. 1
Why This Combination is Problematic
The fundamental issue is that adding sliding scale to 70/30 insulin creates a "reactive" approach layered on top of an already inflexible regimen:
70/30 insulin provides fixed proportions of basal and prandial coverage that cannot be adjusted meal-to-meal based on actual food intake, which is highly variable in hospitalized patients 1
Sliding scale insulin treats hyperglycemia after it has already occurred rather than preventing it, leading to rapid glucose fluctuations and increased risk of both hyper- and hypoglycemia 1
The combination lacks the flexibility needed for patients with poor oral intake, NPO status, or rapidly changing clinical conditions common during hospitalization 1
What Should Be Used Instead
For hospitalized patients requiring insulin, a basal-plus or basal-bolus regimen is strongly preferred over any premixed insulin approach:
Basal-plus regimen (single dose of basal insulin 0.1-0.25 U/kg/day plus correction doses) is preferred for patients with mild hyperglycemia, decreased oral intake, or those undergoing surgery 1, 2
Basal-bolus regimen (basal insulin once or twice daily plus rapid-acting insulin before meals plus correction doses) is preferred for patients with good nutritional intake and established insulin requirements 1
For insulin-naive patients, start with total daily dose of 0.3-0.5 U/kg, with half as basal and half divided before meals, using lower doses (0.1-0.25 U/kg) for high-risk patients including those over 65 years or with renal failure 1
The Limited Role of Sliding Scale Alone
Sliding scale insulin as monotherapy is only appropriate for very specific patient populations:
Patients without diabetes who develop mild stress hyperglycemia during hospitalization 2, 3
Diet-controlled type 2 diabetes patients with good metabolic control at home who develop mild hyperglycemia (can add basal insulin if glucose consistently >180 mg/dL) 2, 3
Sole use of sliding scale is strongly discouraged for patients with established insulin requirements, as it has been shown to be ineffective and leads to worse glycemic control 1
Key Safety Consideration
The risk-benefit calculation strongly favors avoiding premixed insulin in hospitals: While basal-bolus regimens carry a 4-6 times higher risk of hypoglycemia compared to sliding scale alone (RR 5.75 for glucose ≤70 mg/dL), premixed insulin combines this hypoglycemia risk with the inflexibility that makes it particularly dangerous when patients have unpredictable oral intake. 1, 3
Common Pitfall to Avoid
Do not continue home regimens of premixed insulin during hospitalization without converting to a more flexible regimen. The hospital environment with variable food intake, procedures requiring NPO status, and acute illness makes the fixed dosing of premixed insulin inappropriate, regardless of whether sliding scale is added. 1