Anxiety Disorder: This is often the most common cause of excessive sweating and tachycardia without a cardiac origin. Anxiety can lead to the activation of the body's "fight or flight" response, resulting in symptoms like sweating and an increased heart rate.

Hyperthyroidism: An overactive thyroid gland can cause an increase in metabolism, leading to symptoms such as excessive sweating, tachycardia, and weight loss. This condition is relatively common and should be considered in the differential diagnosis.
Hypoglycemia: Low blood sugar can cause the body to release stress hormones like adrenaline, leading to sweating and tachycardia. This is a common issue in diabetic patients but can also occur in non-diabetic individuals under certain circumstances.
Infections: Certain infections, particularly those causing sepsis, can lead to systemic inflammation, sweating, and tachycardia. The body's response to infection can mimic other conditions, making diagnosis challenging.

Pheochromocytoma: A rare tumor of the adrenal gland that produces excess adrenaline, leading to episodes of hypertension, tachycardia, sweating, and other symptoms. Although rare, missing this diagnosis can be fatal due to the risk of hypertensive crises.
Thyroid Storm: A life-threatening complication of untreated or undertreated hyperthyroidism, characterized by extreme symptoms such as very high fever, confusion, and severe tachycardia. Early recognition is crucial for survival.
Neuroleptic Malignant Syndrome (NMS): A rare but life-threatening side effect of neuroleptic medications, characterized by fever, muscle stiffness, and altered mental status, which can also present with tachycardia and sweating.

Carcinoid Syndrome: A condition caused by a rare type of tumor (carcinoid tumor) that secretes serotonin and other chemicals, leading to flushing, sweating, wheezing, and diarrhea, among other symptoms. Tachycardia can occur due to the systemic effects of these chemicals.
Autonomic Dysfunction: Disorders affecting the autonomic nervous system, such as dysautonomia, can lead to a variety of symptoms including orthostatic intolerance, sweating abnormalities, and tachycardia. These conditions are less common and may require specialized testing for diagnosis.