Which advice is most relevant for a client starting oral metronidazole therapy regarding sexual health?

Using condoms until the completion of metronidazole therapy is crucial for a few reasons related to sexual health. Metronidazole is often prescribed for infections that may be transmitted sexually, such as bacterial vaginosis or trichomoniasis. By using condoms, the client helps prevent the transmission of any remaining infection to their partner and reduces the risk of re-infection during and immediately after treatment.

Additionally, this guidance is reinforced by the potential side effects of metronidazole, which can include nausea and other gastrointestinal issues that might affect sexual activity. It's important to ensure both partners are treated and that the infection does not spread or recur during the treatment period.

The other options, while they address different health aspects, do not provide the relevant advice concerning the client's sexual health while undergoing metronidazole therapy. Regular blood pressure checks, discontinuing medication if symptoms worsen, and increasing dietary fiber intake do not directly relate to the immediate concerns regarding safe sexual practices during the treatment period.