Report muscle pain, unusual fatigue, hyperventilation, or abdominal distress (lactic acidosis).
Before you read
Test yourself first: 5 questions
Question 1 of 5
A client taking metformin should be taught to recognize which rare but serious adverse effect?
Answer: A. The most serious adverse effect of metformin is lactic acidosis, which presents with malaise, muscle aches, unusual fatigue, difficulty breathing, and abdominal discomfort. The client should report these symptoms immediately. Metformin alone does not commonly cause hypoglycemia, and weight gain or constipation are not its hallmark serious effects.
Question 2 of 5
A client on metformin is scheduled for surgery with anesthesia. The nurse is aware metformin's serious risk is:
Answer: B. Metformin's rare but serious risk is lactic acidosis, especially with renal impairment, contrast, or hypoperfusion; it is typically held around procedures.
Question 3 of 5
A client taking metformin is scheduled for a contrast-enhanced CT scan with iodinated contrast dye. Which action is the nurse's priority?
Answer: B. Metformin should be withheld at the time of, or before, administration of iodinated contrast and held for 48 hours afterward because contrast-induced kidney injury can lead to metformin accumulation and lactic acidosis. Renal function is rechecked before resuming. The other options do not address this risk.
Question 4 of 5
A client is scheduled for a contrast-enhanced CT scan and takes metformin daily. Which instruction does the nurse reinforce?
Answer: A. Metformin should be withheld at the time of or before iodinated contrast administration and typically for 48 hours afterward, with renal function reassessed before resuming, because contrast-induced renal impairment combined with metformin raises the risk of lactic acidosis.
Question 5 of 5
A client newly started on metformin asks how the drug works. Which statement by the nurse is accurate?
Answer: A. Metformin is a biguanide that lowers glucose mainly by decreasing hepatic glucose production and improving insulin sensitivity; it does not stimulate insulin secretion, so it rarely causes hypoglycemia when used alone. Sulfonylureas, not metformin, increase pancreatic insulin release.
Keep the streak going with more questions like these, each with a full rationale.
What is metformin?
It lowers glucose by decreasing hepatic glucose production and improving insulin sensitivity without causing hypoglycemia on its own. Key principle: hold it around iodinated contrast studies because of the risk of lactic acidosis.
Key points to remember
- Metformin does not cause hypoglycemia when used alone because it does not increase insulin secretion.
- It must be held for 48 hours before and after IV iodinated contrast to prevent lactic acidosis.
- It is contraindicated in renal impairment, which raises lactic acidosis risk.
- Common GI side effects include nausea, diarrhea, and metallic taste, often improving over time.
- Long-term use can cause vitamin B12 deficiency.
Nursing priorities
- Verify renal function (creatinine, eGFR) before and during therapy.
- Hold the drug before contrast procedures and confirm renal function before restarting.
- Monitor blood glucose and A1C for therapeutic response.
- Assess for signs of lactic acidosis: muscle pain, weakness, fatigue, and trouble breathing.
- Administer with meals to reduce GI upset.
Labs & values
Patient teaching
- Take with food to limit nausea and diarrhea.
- Avoid excessive alcohol, which increases lactic acidosis risk.
- Continue diet and exercise; it controls but does not cure diabetes.
Red flags: report now
- Report muscle pain, unusual fatigue, hyperventilation, or abdominal distress (lactic acidosis).
- Never give within 48 hours of IV contrast without renal clearance.
- Report worsening kidney function.
References
Clinical references for this topic
