Humalog (Insulin Lispro)
insulin lispro
Indications for Insulin Lispro
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Type 1 diabetes mellitus | Adults and pediatric patients ≥3 years | Mealtime (bolus) insulin in basal-bolus regimen or CSII pump therapy | FDA Approved |
| Type 2 diabetes mellitus | Adults | Mealtime insulin adjunctive to basal insulin and/or oral agents | FDA Approved |
Insulin lispro received initial FDA approval in June 1996 as the first commercially available rapid-acting insulin analog. It is equipotent to regular human insulin on a unit-for-unit basis but offers significantly faster onset, earlier peak, and shorter duration of action, allowing administration within 15 minutes before or immediately after a meal rather than the 30–60 minutes required with regular insulin. In type 1 diabetes, insulin lispro is used as the mealtime bolus component of a basal-bolus regimen or via continuous subcutaneous insulin infusion (CSII) pump. In type 2 diabetes, it is added to basal insulin therapy when postprandial glucose control is insufficient. Insulin lispro may also be administered intravenously under medical supervision for hospital-based glucose management (FDA PI).
Mild-to-moderate diabetic ketoacidosis (DKA): Subcutaneous insulin lispro has been studied as an alternative to IV regular insulin in mild-to-moderate DKA. Studies show comparable outcomes in selected patients in non-ICU settings. Evidence quality: Moderate.
Gestational diabetes mellitus: Published data have not reported an association between insulin lispro and major birth defects or adverse outcomes. Used frequently when rapid-acting mealtime insulin is needed during pregnancy. Evidence quality: Moderate.
Hyperkalemia (IV): Combined with dextrose for acute treatment of hyperkalemia by driving potassium intracellularly. Evidence quality: Low (extrapolated from insulin class effect).
Dosing of Insulin Lispro
Adult Dosing by Clinical Scenario
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| T1DM — basal-bolus, mealtime coverage | ~50% of total daily dose divided across meals | Individualized by ICR and correction factor | No fixed ceiling | Total daily insulin: typically 0.5–1 unit/kg/day Inject within 15 min before meal or immediately after |
| T1DM — insulin pump (CSII) | ~50% of total daily dose as basal rate; boluses per meal | Programmed basal rates + meal boluses via ICR | No fixed ceiling | U-100 only for pump use; change reservoir every 7 days Do NOT mix with other insulins in pump; do NOT exceed 98.6°F (37°C) |
| T2DM — adding mealtime insulin to basal regimen | 4 units or 10% of basal dose once daily at largest meal | Titrate by 1–2 units or 10–15% twice weekly | No fixed ceiling | If HbA1c <8%, consider reducing basal by 4 units or 10% when starting bolus Advance to additional meals as needed (basal-plus → basal-bolus) |
| T2DM — full basal-bolus intensification | Divide mealtime insulin across 3 meals | Titrate per pre-meal and 2-h postprandial glucose | No fixed ceiling | Total daily dose often 0.5–1.2 units/kg/day depending on insulin resistance Obese patients may require 0.8–1.2 units/kg/day total |
| IV insulin infusion (hospital setting) | Dilute to 0.1–1.0 unit/mL in 0.9% NaCl | Per institutional protocol | Protocol-dependent | Under medical supervision only; monitor glucose and potassium closely Equipotent to regular human insulin IV |
| High-dose requirement (U-200) | Same unit dose as U-100 | Delivers same dose in half the volume | No fixed ceiling | U-200 KwikPen only; do NOT transfer to syringe; do NOT use in pump Dose window shows units; no conversion needed |
Pediatric Dosing (≥3 Years, Type 1 Diabetes)
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| T1DM — mealtime coverage (SC or pump) | Individualized; total daily 0.5–1 unit/kg/day typical | By ICR and correction factor; ≤1.2 units/kg/day during growth spurts | No fixed ceiling | Inject within 15 min before meal or immediately after Not studied in children <3 years or in pediatric T2DM |
In patients using carbohydrate counting, the insulin-to-carbohydrate ratio (ICR) is commonly estimated using the “500 rule” (500 ÷ total daily dose = grams of carbohydrate covered per 1 unit). The correction factor (sensitivity factor) is estimated using the “1800 rule” (1800 ÷ total daily dose = expected glucose drop in mg/dL per 1 unit). Both should be individualized and validated against postprandial glucose data. One unit of insulin lispro is equipotent to one unit of regular human insulin in glucose-lowering effect, but with a faster onset and shorter duration that more closely matches postprandial glucose excursions (FDA PI, ADA 2025).
Humalog U-100 may be mixed with NPH insulin (Humulin N) in the same syringe. Draw insulin lispro into the syringe first to prevent clouding by the longer-acting NPH. The mixture should be injected immediately after mixing. Do NOT mix insulin lispro with any other insulin when used in a pump or when administering intravenously. Humalog U-200 must NOT be mixed with any other insulin (FDA PI).
Pharmacology of Insulin Lispro
Mechanism of Action
Insulin lispro is a recombinant human insulin analog produced in Escherichia coli. It differs from native human insulin by the reversal of the amino acids proline (B28) and lysine (B29) on the B-chain. This transposition reduces the tendency of insulin molecules to self-associate into stable hexamers at the injection site, resulting in approximately 300-fold reduction in dimerization affinity. After subcutaneous injection, insulin lispro hexamers dissociate into monomers much more rapidly than regular human insulin, leading to faster absorption into the bloodstream. Once circulating, insulin lispro binds to the insulin receptor with affinity essentially identical to endogenous human insulin, activating the PI3K/Akt pathway to stimulate glucose uptake into skeletal muscle and adipose tissue, promote glycogen synthesis, suppress hepatic glucose production, and inhibit lipolysis and proteolysis. Its rapid onset and short duration make it the preferred mealtime insulin for controlling postprandial glucose excursions.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Onset ~15 min; Tmax 30–90 min; bioavailability 55–77% (SC, dose-dependent); faster absorption from abdominal sites | Rapid hexamer-to-monomer dissociation enables mealtime administration (within 15 min before or immediately after eating); less variability between injection sites than regular insulin |
| Distribution | Vd 0.72–1.55 L/kg (inversely dose-dependent) | Dose-dependent Vd reflects saturable tissue binding; distributes differently from regular human insulin at varying doses |
| Metabolism | Kidneys ~60%, liver ~30–40% (exogenous SC route); identical to human insulin degradation | No CYP involvement; exogenous route bypasses hepatic first pass, shifting primary degradation to kidneys. In renal impairment, insulin sensitivity increases and dose reduction may be needed |
| Elimination | Duration of action <5 h (usually 2–4 h); half-life ~1 h (SC) | Shorter duration than regular human insulin (~6–8 h); reduces late postprandial hypoglycemia risk; covers mealtime glucose excursion without prolonged tail |
Side Effects of Insulin Lispro
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Hypoglycemia (any severity) | Most common adverse reaction overall | Rate depends on dose, glycemic targets, and concomitant medications. In T1DM trials with Admelog, severe hypoglycemia (requiring third-party assistance) occurred in 13.5% at 52 weeks |
| Nasopharyngitis | ≥5% | Reported in T1DM trials (Admelog PI Table 1); background infection rate comparable to comparator |
| Upper respiratory tract infection | ≥5% | Reported in T1DM trials; not considered causally related to insulin therapy |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Injection site reactions | 3–5% | Pain, redness, swelling, itching at injection site; mitigated by site rotation and room-temperature insulin |
| Weight gain | 1–5% | Anabolic effects of insulin and decreased glucosuria; common to all insulins |
| Lipodystrophy | 1–2% | Lipohypertrophy or lipoatrophy from repeated injection at same site; alters insulin absorption |
| Pruritus / Rash | 1–3% | May be localized or generalized; rates similar to regular human insulin in clinical trials |
| Headache | ≥5% (T1DM trials) | Generally transient; comparable to comparator insulin in head-to-head studies |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Severe hypoglycemia | 13.5% T1DM at 52 wk; 2.4% T2DM at 26 wk | 30 min–4 h post-injection (peak action window) | Oral glucose, glucagon, or IV dextrose; assess precipitating factors; adjust dose or timing |
| Anaphylaxis / severe allergic reaction | Rare | Minutes to hours after injection | Emergency treatment; permanent discontinuation of insulin lispro |
| Hypokalemia | Uncommon (dose-related) | Hours after large doses or with potassium-lowering drugs | Monitor potassium; supplement as needed; especially important with IV use |
| Heart failure exacerbation (with TZDs) | Uncommon | Weeks to months | Monitor for fluid retention; reduce or discontinue TZD if signs develop |
| Hyperglycemia/DKA from pump malfunction | Uncommon | Hours after pump failure (no basal insulin backup) | Switch to SC injection immediately; troubleshoot pump; monitor ketones |
Because insulin lispro has a rapid onset (~15 min) and short duration (<5 h), the window of greatest hypoglycemia risk is during the first 1–4 hours after injection, coinciding with its peak action. Compared with regular human insulin, insulin lispro causes less late postprandial hypoglycemia (3–6 hours post-meal) because its glucose-lowering effect dissipates more quickly. Key risk factors include skipping or delaying meals after injection, exercising within the post-injection window, and alcohol consumption. Patients should always carry a fast-acting glucose source and understand the “15–15 rule” (consume 15 g of carbohydrate, recheck in 15 minutes).
Drug Interactions with Insulin Lispro
Insulin lispro is metabolized primarily by the kidneys and liver through proteolytic degradation, with no CYP enzyme involvement. Drug interactions are pharmacodynamic, affecting glucose metabolism or masking hypoglycemia symptoms.
Monitoring for Insulin Lispro
-
Blood Glucose
Pre-meal, 2-h postprandial; per ADA targets
Routine Postprandial monitoring is essential for mealtime insulin titration. CGM recommended when available. ADA 2025 targets: pre-meal 80–130 mg/dL; 2-h postprandial <180 mg/dL. -
HbA1c
Every 3 months until stable, then every 6 months
Routine Individualized targets per ADA 2025. Insulin lispro primarily improves postprandial contribution to HbA1c. -
Potassium
With IV use; periodically with SC in at-risk patients
Trigger-based All insulins drive potassium intracellularly. Especially important during IV infusion and in patients on diuretics or digoxin. -
Renal Function
Baseline, then per ADA guidelines
Routine Insulin sensitivity increases in declining renal function. Dose reduction may be needed to prevent hypoglycemia. -
Injection / Infusion Sites
Every visit; pump sites per manufacturer
Routine Inspect for lipodystrophy and cutaneous amyloidosis. For pump users, change infusion set and site per manufacturer instructions. -
Pump Function
Continuous (for CSII users)
Routine Pump malfunction can cause rapid hyperglycemia and DKA because insulin lispro has no basal depot effect. Patients must have backup SC injection supplies and know how to recognize pump failure. -
Anti-Insulin Antibodies
Not routinely measured
Trigger-based In clinical trials, antibody levels peaked by 12 months and declined thereafter with no apparent impact on glycemic control or insulin dose requirements (FDA PI).
Contraindications & Cautions for Insulin Lispro
Absolute Contraindications
- During episodes of hypoglycemia — do not administer while blood glucose is below normal range.
- Hypersensitivity to insulin lispro or any excipient (m-cresol, glycerol, zinc oxide, dibasic sodium phosphate) — anaphylaxis has been reported.
Relative Contraindications (Specialist Input Recommended)
- Insulin pump use with U-200 — Humalog U-200 must NOT be used in insulin pumps. Only U-100 is approved for CSII.
- Transferring U-200 from KwikPen to syringe — syringe markings will not measure the dose correctly, risking severe overdose and life-threatening hypoglycemia.
- Significant heart failure (NYHA III–IV) with TZDs — combination increases fluid retention risk.
Use with Caution
- Renal impairment — increased insulin sensitivity as renal function declines; dose reduction and closer monitoring needed.
- Hepatic impairment — no PK change per FDA PI, but impaired gluconeogenesis may increase hypoglycemia risk.
- Elderly patients (≥65 years) — conservative dosing recommended to reduce hypoglycemia risk.
- Hypoglycemia unawareness — patients who cannot recognize warning signs require CGM and may need relaxed glycemic targets.
- Mixing insulins — U-100 may be mixed with NPH only; draw lispro first. Never mix U-200 with anything.
Accidental mix-ups between insulin products and between U-100 and U-200 concentrations have been reported. Patients must always verify the insulin label and concentration before each injection. Do NOT transfer Humalog U-200 from the KwikPen into a syringe — the markings on the syringe will not measure the dose correctly and can result in overdosage and severe hypoglycemia. Never share pens, cartridges, syringes, or needles between patients due to the risk of blood-borne pathogen transmission (FDA PI).
Patient Counselling for Insulin Lispro
Purpose of Therapy
Insulin lispro is a fast-acting mealtime insulin that helps control the rise in blood sugar that occurs when you eat. It is used alongside a longer-acting (basal) insulin or in an insulin pump to provide complete blood sugar management throughout the day. Unlike your basal insulin which works in the background, insulin lispro covers each individual meal and works within 15 minutes.
How to Take
Inject insulin lispro within 15 minutes before eating or immediately after a meal, into the abdomen, thigh, upper arm, or buttocks. Rotate injection sites. For pump users, follow the pump manufacturer instructions and change the reservoir at least every 7 days. The solution should appear clear and colorless. Store unopened vials and pens in the refrigerator; once in use, store at room temperature (below 30°C / 86°F) for up to 28 days.
Sources
- Eli Lilly and Company. Humalog (insulin lispro) injection, for subcutaneous or intravenous use. Full Prescribing Information. Indianapolis, IN; Revised 2025. FDA Label (PDF) Primary regulatory reference for all dosing, indications, contraindications, adverse effects, and pharmacokinetic data.
- Eli Lilly and Company. Insulin Lispro injection prescribing information. Lilly PI Authorized generic (unbranded) insulin lispro prescribing information with identical clinical content to Humalog label.
- Sanofi-Aventis. Admelog (insulin lispro injection) prescribing information. DailyMed Biosimilar (follow-on) insulin lispro PI with severe hypoglycemia incidence data (13.5% T1DM, 2.4% T2DM) from the SORELLA program.
- Anderson JH Jr, Brunelle RL, Koivisto VA, et al. Reduction of postprandial hyperglycemia and frequency of hypoglycemia in IDDM patients on insulin-analog treatment. Diabetes. 1997;46(2):265-270. doi:10.2337/diab.46.2.265 Pivotal 6-month crossover trial (n=1,008) in T1DM demonstrating superior postprandial glucose control and modest HbA1c improvement with insulin lispro vs regular human insulin.
- Garg SK, Rosenstock J, Ways K. Optimized Basal-Bolus Insulin Regimens in Type 1 Diabetes: Insulin Glulisine Versus Regular Human Insulin in Combination With Basal Insulin Glargine. Endocr Pract. 2005;11(1):11-17. doi:10.4158/EP.11.1.11 Comparative basal-bolus trial informing the clinical positioning of rapid-acting analogs including lispro within modern basal-bolus regimens.
- Umpierrez GE, Cuervo R, Karabell A, et al. Treatment of diabetic ketoacidosis with subcutaneous insulin aspart. Diabetes Care. 2004;27(8):1873-1878. doi:10.2337/diacare.27.8.1873 Evidence supporting SC rapid-acting insulin analogs (including lispro) for mild-to-moderate DKA management in non-ICU settings.
- American Diabetes Association Professional Practice Committee. 9. Pharmacologic Approaches to Glycemic Treatment: Standards of Care in Diabetes—2025. Diabetes Care. 2025;48(Suppl 1):S181-S206. doi:10.2337/dc25-S009 Current ADA guidelines for mealtime insulin selection, carbohydrate counting, correction dosing, and insulin pump management.
- Samson SL, Vellanki P, Blonde L, et al. American Association of Clinical Endocrinology Consensus Statement: Comprehensive Type 2 Diabetes Management Algorithm—2023 Update. Endocr Pract. 2023;29(5):305-340. doi:10.1016/j.eprac.2023.02.001 AACE algorithm positioning rapid-acting insulin analogs in stepwise intensification from basal-only to basal-bolus therapy in T2DM.
- Howey DC, Bowsher RR, Brunelle RL, et al. [Lys(B28),Pro(B29)]-human insulin: a rapidly absorbed analogue of human insulin. Diabetes. 1994;43(3):396-402. doi:10.2337/diab.43.3.396 Foundational PK/PD study establishing that the B28-B29 amino acid transposition produces faster absorption and earlier peak than regular human insulin.
- Brems DN, Alter LA, Beckage MJ, et al. Altering the association properties of insulin by amino acid replacement. Protein Eng. 1992;5(6):527-533. doi:10.1093/protein/5.6.527 Structural biology study explaining how the Pro-Lys reversal at B28–B29 reduces hexamer stability and accelerates monomer dissociation at the injection site.
- Islam N, Khanna NR, Patel P, et al. Insulin Lispro. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; Updated 2024 Feb 28. StatPearls Comprehensive review of insulin lispro pharmacokinetics including bioavailability (55–77%), dose-dependent Vd, and metabolism distribution between kidneys and liver.
- Holleman F, Hoekstra JBL. Insulin lispro. N Engl J Med. 1997;337(3):176-183. doi:10.1056/NEJM199707173370307 NEJM review article providing clinical context for insulin lispro’s pharmacological advantages over regular human insulin in mealtime glycemic control.
- Mudaliar SR, Lindberg FA, Joyce M, et al. Insulin aspart (B28 Asp-insulin): a fast-acting analog of human insulin — absorption kinetics and action profile compared with regular human insulin in healthy nondiabetic subjects. Diabetes Care. 1999;22(9):1501-1506. doi:10.2337/diacare.22.9.1501 Comparative PK study providing context for insulin lispro within the rapid-acting analog class alongside insulin aspart.