Which laboratory test should the nurse monitor for a client on isoniazid therapy?

When a client is on isoniazid therapy, monitoring liver function tests is crucial because isoniazid, an antibiotic used primarily for the treatment of tuberculosis, can have hepatotoxic effects. The liver metabolizes isoniazid, and in some individuals, particularly those who may have pre-existing liver disease or those who consume alcohol, this medication can lead to an increased risk of liver damage. Regular monitoring of liver function tests can help detect any early signs of hepatotoxicity, allowing for timely intervention if needed.

Blood glucose levels, kidney function tests, and complete blood counts, while important in various clinical contexts, do not have the same direct association with isoniazid therapy as liver function tests. Isoniazid does not directly affect glucose metabolism or kidney function in a significant way, and while it can lead to some hematologic changes, liver monitoring is prioritized due to the potential severity of hepatotoxic effects.