Section 13.1
Antidiabetic Medications & Glucagon
Compare insulin, metformin, insulin secretagogues, GLP-1 therapy and glucagon, then use mechanism and patient context to prevent or respond to hypoglycemia and treatment-specific hazards.
Learn
Idea 1 / 3
Insulin timing must match physiology
Basal insulin restrains glucose production between meals and overnight; prandial insulin covers meal-related glucose entry. Rapid-acting insulin without the expected carbohydrate intake, or an unplanned increase in activity, can produce dangerous hypoglycemia. Insulin also shifts potassium into cells, so hypokalemia is an additional concern in high-risk or intravenous use.
If a meal is delayed after rapid insulin, sweating, tremor or confusion should trigger immediate glucose assessment and the prescribed hypoglycemia plan.
Read all essential notes
Insulin timing must match physiology
Basal insulin restrains glucose production between meals and overnight; prandial insulin covers meal-related glucose entry. Rapid-acting insulin without the expected carbohydrate intake, or an unplanned increase in activity, can produce dangerous hypoglycemia. Insulin also shifts potassium into cells, so hypokalemia is an additional concern in high-risk or intravenous use.
If a meal is delayed after rapid insulin, sweating, tremor or confusion should trigger immediate glucose assessment and the prescribed hypoglycemia plan.
Glucose-lowering mechanisms carry different risks
Metformin primarily reduces hepatic glucose production and usually does not cause hypoglycemia alone, but renal impairment and hypoxic states increase concern for rare lactic acidosis. Sulfonylureas stimulate insulin release and can cause prolonged hypoglycemia. GLP-1 receptor agonists enhance glucose-dependent insulin secretion, slow gastric emptying and reduce appetite; hypoglycemia risk rises when combined with insulin or an insulin secretagogue.
A low glucose after adding a GLP-1 agent to insulin should prompt review of the combined regimen, not the claim that GLP-1 therapy can never contribute.
Rescue and contrast plans are conditional
Glucagon mobilizes hepatic glycogen for severe hypoglycemia when a person cannot safely take oral carbohydrate; caregivers should give it according to the product plan, call emergency help and provide oral carbohydrate after recovery. The legacy rule to stop metformin before every iodinated-contrast study is too broad: current labeling targets specific renal, hepatic, alcohol, heart-failure and intra-arterial-contrast situations, with renal reassessment before restart.
An unconscious person should not be forced to swallow; use prescribed rescue glucagon and emergency services.
Common misconception: “Metformin must always be stopped for any contrast study” is outdated and overbroad; follow current product criteria and the imaging team’s individualized renal-risk plan.
Explore
Interactive mechanism plate · 13.1
Glucose medicines act at different control points
Place insulin, insulin secretion, metformin/GLP-1 pathways and glucagon on a pancreas–blood–liver map to connect benefit to hypoglycemia risk.
More controls
1 / 3 · Insulin lowers circulating glucose by supporting uptake and storage · Schematic, not to scale; arrows show causal teaching relationships.
Reduced motion is on: use the manual controls to inspect each causal change.
Go deeper: worked example
A patient receives rapid-acting insulin, cannot eat because of vomiting, then becomes confused and cannot safely swallow.
- Recognize severe hypoglycemia risk and check glucose if this does not delay rescue.
- Do not give oral food or fluid to a person who cannot swallow safely; administer the prescribed glucagon rescue and call emergency assistance.
- Once awake and able to swallow, give oral carbohydrate and investigate the insulin–meal mismatch to prevent recurrence.
Rescue corrects the immediate glucose emergency; medication and meal review corrects the cause.
Explain it yourself
Why does glucagon sometimes fail after prolonged starvation?
Reveal explanation
Its rescue effect depends on mobilizing hepatic glycogen; severely depleted stores leave little substrate to release as glucose.
Create and evaluate
Create a safe diabetes-medication plan for meals, illness, procedures and severe hypoglycemia.
Formative activity: compare your reasoning with the rubric. This response is not automatically graded and does not award mastery. It remains only on this page and is cleared when you leave.
Compare with the rubric and example
- Matches each drug’s mechanism and timing to meals and glucose monitoring.
- Identifies hypoglycemia, renal, contrast and interaction contingencies.
- Defines caregiver rescue steps and post-recovery prevention.
Coordinate rapid insulin with food, never improvise insulin changes during illness, monitor more often when intake or activity changes, apply current metformin contrast criteria, teach caregivers to use glucagon without forcing oral intake, call emergency help, then give carbohydrate after safe recovery.
Sources and review status
Educational draft. Medical and French-language expert review pending. External sources require an internet connection; essential explanations are included above.
- DailyMed: insulin lispro prescribing information
Hypoglycemia, meal/activity changes, medication errors and hypokalemia
- DailyMed: metformin prescribing information
Renal criteria, lactic acidosis risk and iodinated-contrast procedure instructions
- DailyMed: semaglutide (Ozempic) prescribing information
GLP-1 mechanism-related precautions and hypoglycemia with insulin or secretagogues
- DailyMed: glucagon nasal powder prescribing information
Severe-hypoglycemia rescue, emergency assistance, oral carbohydrate and glycogen dependence
Check my understanding
Mastery Question Gate
Answer all questions correctly to unlock the next lesson. Retakes vary the selection when enough questions are available; some questions may repeat.
1. Why must Metformin be temporarily discontinued prior to procedures requiring IV iodinated contrast dye?