Which of the following blood tests could be ordered for the workup of insomnia?

Ordering a ferritin test for the workup of insomnia is particularly relevant because ferritin is a marker for iron stores in the body, and low levels can indicate iron deficiency. Iron deficiency has been associated with sleep disturbances, including insomnia. This is particularly significant in populations at risk of iron deficiency, such as women of childbearing age or individuals with certain dietary restrictions.

In assessing insomnia, it is important to consider potential underlying causes, including nutritional deficiencies. Low iron levels can lead to restless leg syndrome or other sleep-related issues, thereby contributing to difficulty falling or staying asleep. Therefore, measuring ferritin can provide valuable insights into whether iron deficiency could be affecting the patient's sleep quality.

Other tests among the options may not directly relate to the investigation of insomnia. For example, a complete blood count may help assess for anemia but does not specifically evaluate iron stores. A lipid panel focuses on cholesterol and triglycerides, which are not directly linked to sleep quality. Similarly, a hepatic function panel monitors liver health but does not have specific relevance to insomnia. Thus, measuring ferritin stands out as a pertinent and useful step in evaluating a patient presenting with insomnia.