Which question is the best to assess the seriousness of a client's suicidal ideation?

The question that best assesses the seriousness of a client's suicidal ideation is one that directly probes the specifics of a person's plans regarding self-harm. Asking about how they are planning to harm themselves provides critical information about the intent, means, and immediacy of their suicidal thoughts.

By inquiring about the methods they are considering, a clinician can gauge the level of danger the client might be in. This type of question can also reveal any preparatory actions that the individual may have taken, indicating a higher level of risk.

In contrast, while questions about making a will, family awareness of the situation, or the duration of suicidal thoughts can give contextual information about the individual's state of mind or support system, they do not directly address the specific intent or planning involved in a potential suicide attempt. Therefore, while they can be relevant in a broader evaluation, they do not provide the precise insights necessary for assessing the immediate risk of self-harm as effectively as a direct question about their planned method.