For a 66‑year‑old male with type 2 diabetes, weight 84 kg, NPO during the day and receiving tube feeds from 1600 to 0800, on insulin glargine (Lantus) 22 units at 1700 and prednisone 20 mg at 0800, with an insulin‑sensitivity factor of 15 mg/dL at 1600 and 2000, and blood glucose of 199 mg/dL at 1600 and 244 mg/dL at 2000, what fixed dose of rapid‑acting insulin aspart (Novolog) should be administered at 1600 and what dose of intermediate‑acting insulin (NPH) should be given at 2000?

Insulin Dosing Recommendations for Tube Feeding with Prednisone

For this patient on continuous tube feeds from 1600-0800 with morning prednisone 20 mg, I recommend increasing the fixed Novolog dose at 1600 to approximately 35-40 units and increasing the NPH dose at 2000 to approximately 85-90 units.

Clinical Context and Rationale

This patient demonstrates persistent hyperglycemia (199-244 mg/dL range) despite receiving substantial insulin doses. The current regimen of 28 units Novolog at 1600 and 74 units NPH at 2000 is insufficient. The blood glucose pattern shows:

• Elevated morning values (224 mg/dL at 0800) despite overnight NPH coverage
• Persistent elevation at tube feed initiation (199 mg/dL at 1600)
• Peak at 2000 (244 mg/dL) when prednisone effect is maximal
• Overnight values remaining elevated (209-223 mg/dL)

Specific Dose Calculations

Novolog at 1600 (Tube Feed Initiation)

The current 28 units is inadequate. Using guideline-based calculations 1:

• Carbohydrate-based dosing: For continuous tube feeds, calculate 1 unit per 10-15 g carbohydrate 1, 2
• Assuming standard tube feed formula running 16 hours (1600-0800), estimate total carbohydrate load
• Current dose increase: The 1600 BG of 199 mg/dL requires correction plus nutritional coverage
• Recommended: Increase to 35-40 units Novolog at 1600

This represents approximately a 25-35% increase from current dosing, accounting for both the nutritional load and the prednisone effect that peaks 4-8 hours after morning administration 2.

NPH at 2000

The 2000 NPH dose is critical because:

1. Prednisone timing: Morning prednisone 20 mg peaks 4-8 hours later (1200-1600) but has pharmacologic effects lasting through the day 2
2. NPH profile matches steroid effect: NPH administered concomitantly with intermediate-acting steroids provides appropriate coverage 3
3. Current inadequacy: BG at 2000 is 244 mg/dL, and overnight values remain 209-223 mg/dL despite 74 units NPH

Recommended: Increase to 85-90 units NPH at 2000

This represents approximately a 15-20% increase. The guideline specifically states that for higher doses of glucocorticoids, increasing doses of prandial and correctional insulin "sometimes as much as 40-60% or more" may be needed 3. However, given the overnight tube feeding and risk of nocturnal hypoglycemia, a more conservative 15-20% increase is prudent initially.

Critical Considerations for Prednisone-Induced Hyperglycemia

NPH is the preferred insulin for once-daily intermediate-acting glucocorticoids like prednisone 2, 4, 2, 3. The guidelines explicitly state: "Once-a-day, short-acting glucocorticoids such as prednisone peak in about 4-8 h, so coverage with intermediate-acting (NPH) insulin may be sufficient" 2.

The current Lantus 22 units at 1700 should be continued as it provides baseline basal coverage, but the NPH at 2000 specifically targets the prednisone-induced hyperglycemia pattern 3.

Tube Feeding Insulin Strategy

For continuous enteral feeds, the approach should include 1, 2:

• Basal insulin: Continue prior basal (Lantus 22 units) - this is appropriate
• Nutritional insulin: The Novolog at 1600 serves as the primary nutritional coverage for the 16-hour feed
• NPH overlay: The 2000 NPH provides both steroid coverage and additional nutritional support through the night

The guideline recommends "NPH insulin administered with the initiation of feeding represents a reasonable approach to cover this nutritional load" for nocturnal tube feeding 1. However, in this case, the NPH is administered at 2000 (4 hours after feed start) which still provides appropriate coverage given its 4-6 hour peak 3.

Monitoring and Titration

Daily adjustments are essential 3. The guidelines emphasize: "Whatever orders are started, adjustments based on anticipated changes in glucocorticoid dosing and POC glucose test results are critical" 2.

Target range should be 100-180 mg/dL 3. Current values are consistently above this range, justifying dose increases.

Adjustment Algorithm:

• If 50% of BG values remain >180 mg/dL after 2-3 days: increase Novolog by 10% (4 units) and NPH by 10% (9 units)
• If any BG <80 mg/dL: reduce corresponding insulin by 10-20% 4
• Monitor particularly for overnight hypoglycemia given the NPH peak occurs 4-6 hours post-administration 3

Common Pitfalls to Avoid

1. Under-dosing for steroid effect: The insulin-to-steroid ratio may need to be 0.40 units/mg prednisone or higher 5. Current dosing (total ~124 units/20 mg = 0.62 units/mg) is reasonable but distribution needs optimization.

2. Ignoring the diurnal pattern: Prednisone causes disproportionate daytime hyperglycemia 6, 7. The 2000 NPH specifically addresses this.

3. Discontinuing tube feeds without glucose support: If feeds are interrupted, immediately start 10% dextrose to prevent hypoglycemia 1, 3.

4. Using only long-acting insulin: Glargine alone is insufficient for prednisone-induced hyperglycemia 6, 7. NPH is superior for matching the steroid effect profile.

The evidence strongly supports using NPH for intermediate-acting glucocorticoid coverage 2, 4, 2, 3, and the current regimen appropriately includes this. The doses simply need upward titration based on persistent hyperglycemia.