Which phrase is not considered a red flag requiring immediate medical action?

The phrase "paresthesias" refers to sensations such as tingling, prickling, or numbness that can occur in various conditions. While it can indicate an underlying issue that might need assessment, it is not inherently indicative of an immediate medical emergency. Paresthesias can result from a variety of causes, ranging from benign conditions, like temporary nerve compression, to more serious issues like multiple sclerosis or diabetes. However, it often does not present as a life-threatening situation that necessitates immediate action.

In contrast, the other options refer to symptoms that are widely recognized as red flags. Lethargy in a young child could signify an underlying infection or other serious condition that requires prompt evaluation. The description "worst headache of my life" suggests a potential for life-threatening conditions, such as a subarachnoid hemorrhage. Tearing back pain between the shoulder blades in an older adult raises concerns for aortic dissection, which is a surgical emergency. Thus, the phrase that does not suggest an urgent medical condition is paresthesias, allowing for a less immediate approach to investigation and management.