What is the primary effect of steroids on patients that must be considered before treatment?

The primary effect of steroids on patients that needs to be taken into account before treatment is immunosuppression. Corticosteroids are known to suppress the immune system, which can increase the risk of infections and delay wound healing. This is particularly crucial to consider when treating patients who may already be at risk, such as those with autoimmune diseases, post-surgical patients, or those with existing infections.

Immunosuppression occurs because steroids inhibit the functioning of white blood cells, which are critical for the body's immune response. This effect can lead to higher susceptibility to pathogens and complications during and after treatment. Therefore, understanding this consequence is essential for healthcare providers to properly manage and monitor patients receiving steroid therapy, ensuring appropriate precautions are taken to mitigate potential risks.

The other options, such as reduced appetite, increased energy levels, and weight loss, may occur in some patients and contexts but do not have the broad and immediate public health implications of immunosuppression when steroids are used. Thus, while these effects may be relevant in specific cases, immunosuppression stands out as the foremost concern to be addressed prior to treatment.