Final answer:
The critical information for the healthcare provider is that the patient is supplementing with St. John's wort, which can interfere with antiretroviral drugs and impact HIV treatment effectiveness.
Step-by-step explanation:
The most important information to communicate to the healthcare provider about a patient taking antiretroviral medication and feeling depressed and anxious is that the patient takes vitamin supplements and St. John's wort. St. John's wort is known to interact with many medications, including antiretroviral drugs, potentially reducing their effectiveness. This interaction can lead to an increase in viral load and decrease in CD4 T-cell count, thus undermining the management of the HIV infection.