Final answer:
The nurse should review the hematocrit and sodium level lab results before administering doxycycline to a client with syphilis.
Step-by-step explanation:
The nurse should review the hematocrit and sodium level lab results before administering doxycycline to a client who has syphilis. The hematocrit test measures the percentage of red blood cells in the blood and can help determine if the client has anemia, which may affect the dosage of the medication. The sodium level test measures the amount of sodium in the blood and can indicate if the client has any electrolyte imbalances that may affect the administration of the medication.