The short answer
Pharmacologic niacin may worsen glucose control during Humalog premix treatment. That supports monitoring, but it does not establish a niacin requirement or protective spacing interval.
What this answer covers
Oral niacin, especially high-dose nicotinic acid; ordinary dietary vitamin B3 and nicotinamide differ. Whole Humalog Mix75/25 or Mix50/50 product scope.
- Supplement or preparation
- Niacin
- Medication ingredient
- insulin lispro protamine, human
Both product labels name niacin
Humalog Mix75/25 and Mix50/50 list niacin as potentially reducing their glucose-lowering effect. More frequent monitoring and clinician-directed treatment review may be needed.
The clinical trial used a high-dose combination
A large trial of extended-release niacin with laropiprant found more serious disturbances in diabetes control. It did not isolate this insulin component or study ordinary nutritional niacin doses.
No nutrient need or protective gap follows
Neither the trial nor the labels show that taking lispro premix creates a need for niacin. A short interval between doses has not been established to prevent a systemic glucose effect.
Review supplement changes
Discuss starting or stopping pharmacologic niacin with the diabetes team and review glucose readings. Do not alter insulin independently; a fixed premix does not allow separate adjustment of the protamine fraction.
Evidence and practical considerations
Timing & monitoring
No established supplement requirement or protective spacing interval with the exact lispro premix; glucose monitoring does not demonstrate a nutrient need.
- Exact scope
- Oral niacin, especially high-dose nicotinic acid; ordinary dietary vitamin B3 and nicotinamide differ. Whole Humalog Mix75/25 or Mix50/50 product scope. with Insulin lispro protamine human RxCUI314684 IN within HumalogMix75/25 or50/50, SC only.
- Medication form and route
- subcutaneous insulin premix; oral supplement
What remains uncertain
- Whole-product evidence does not isolate protamine component; no exact event rate or universal dose change.
Factors that may matter: Fixed ratio; Meals; Product; Dose; Other diabetes treatment.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Adults prescribed the fixed lispro premix
Hypoglycemia can be severe; niacin can reduce glucose lowering. Fixed ratio precludes separate basal/prandial dose adjustments. Inject within15minutes before a meal as labeled.
How this applies: RxCUI314684 IN insulin lispro protamine, human, as component of specified Humalog mixture.
Whole-product evidence does not isolate protamine component, compare every premix or apply to soluble lispro alone. No herb-specific adverse-event rate.
Source 2: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Adults prescribed the fixed lispro premix
Hypoglycemia can be severe; niacin can reduce glucose lowering. Fixed ratio precludes separate basal/prandial dose adjustments. Inject within15minutes before a meal as labeled.
How this applies: RxCUI314684 IN insulin lispro protamine, human, as component of specified Humalog mixture.
Whole-product evidence does not isolate protamine component, compare every premix or apply to soluble lispro alone. No herb-specific adverse-event rate.
Source 3: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 25,673high-vascular-risk adults.
High-dose niacin-laropiprant increased serious disturbances in diabetes control compared with placebo.
How this applies: Indirect for insulin lispro protamine within the labeled Humalog mixtures; original preparation and clinical endpoint retained.
High-dose niacin plus laropiprant; no exact lispro-premix analysis, ordinary dietary dose inference or proven supplement requirement.
Research assessment: · Open full citations ↗
Side effects & toxicity
Both current Humalog premix labels name niacin; precaution applies to the whole product and pharmacologic exposure, not an isolated protamine-component effect.
- Exact scope
- Oral niacin, especially high-dose nicotinic acid; ordinary dietary vitamin B3 and nicotinamide differ. Whole Humalog Mix75/25 or Mix50/50 product scope. with Insulin lispro protamine human RxCUI314684 IN within HumalogMix75/25 or50/50, SC only.
- Medication form and route
- subcutaneous insulin premix; oral supplement
What remains uncertain
- Whole-product evidence does not isolate protamine component; no exact event rate or universal dose change.
Factors that may matter: Fixed ratio; Meals; Product; Dose; Other diabetes treatment.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Adults prescribed the fixed lispro premix
Hypoglycemia can be severe; niacin can reduce glucose lowering. Fixed ratio precludes separate basal/prandial dose adjustments. Inject within15minutes before a meal as labeled.
How this applies: RxCUI314684 IN insulin lispro protamine, human, as component of specified Humalog mixture.
Whole-product evidence does not isolate protamine component, compare every premix or apply to soluble lispro alone. No herb-specific adverse-event rate.
Source 2: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Adults prescribed the fixed lispro premix
Hypoglycemia can be severe; niacin can reduce glucose lowering. Fixed ratio precludes separate basal/prandial dose adjustments. Inject within15minutes before a meal as labeled.
How this applies: RxCUI314684 IN insulin lispro protamine, human, as component of specified Humalog mixture.
Whole-product evidence does not isolate protamine component, compare every premix or apply to soluble lispro alone. No herb-specific adverse-event rate.
Source 3: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 25,673high-vascular-risk adults.
High-dose niacin-laropiprant increased serious disturbances in diabetes control compared with placebo.
How this applies: Indirect for insulin lispro protamine within the labeled Humalog mixtures; original preparation and clinical endpoint retained.
High-dose niacin plus laropiprant; no exact lispro-premix analysis, ordinary dietary dose inference or proven supplement requirement.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Prepared exact protamine-lispro ingredient article with fixed-combination and original case-report limits. | |
| Research summary published |
Article revision: 634fec247eff9b61
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.