Sweating is a natural bodily function primarily used to regulate core temperature. For individuals with diabetes, however, changes in perspiration can signal underlying health issues. Unusual or excessive sweating (hyperhidrosis) is a common symptom that can manifest as profuse sweating at unexpected times or, paradoxically, an inability to sweat in other areas. The disruption of normal sweating patterns in diabetes is often a consequence of fluctuating blood sugar levels or long-term nerve damage.
Sweating Due to Low Blood Sugar
Unexplained or sudden sweating in a person with diabetes is most frequently a physical manifestation of hypoglycemia, or low blood sugar. This occurs when blood glucose levels fall below 70 milligrams per deciliter (mg/dL) and the body initiates a rapid emergency response. The sympathetic nervous system is activated, triggering what is often described as the body’s “fight-or-flight” reaction.
This response involves the adrenal glands releasing hormones, including adrenaline (epinephrine), into the bloodstream. Adrenaline’s primary purpose here is to quickly signal the liver to break down stored glycogen and release glucose to raise blood sugar. The surge of adrenaline also causes a host of physical symptoms, with sweating being one of the most noticeable.
The sweat produced during a hypoglycemic episode is typically cold and clammy, often accompanied by other symptoms like shakiness, a rapid heartbeat, and anxiety. Recognizing this pattern of cold, profuse sweating is important because it signals that the low blood sugar needs immediate treatment with fast-acting carbohydrates.
Autonomic Neuropathy and Sweating Patterns
A more complex and chronic cause of abnormal sweating is a condition called autonomic neuropathy, which is nerve damage resulting from sustained high blood sugar levels over time. Autonomic neuropathy affects the nerves that control involuntary functions, including the sudomotor nerves that regulate the sweat glands. This nerve damage can lead to a dual and confusing pattern of perspiration: excessive sweating in some areas and a complete lack of sweating in others.
Hyperhidrosis, or excessive sweating, often occurs in the upper body, such as the face, neck, and torso, frequently happening at night or in warm environments. This localized excessive sweating is thought to be a compensatory reaction, where the remaining healthy sweat glands work harder to make up for the function lost elsewhere. The disruption essentially causes the sweat-regulating system to misfire, leading to unneeded perspiration.
Conversely, in the lower extremities like the feet and legs, the damaged sudomotor nerves may no longer transmit signals effectively, leading to anhidrosis, or insufficient sweating. This lack of perspiration impairs the body’s ability to cool itself effectively, increasing the risk of overheating and heatstroke. This combination of compensatory upper-body hyperhidrosis and lower-body anhidrosis highlights the complexity of diabetic nerve damage.
Other Triggers for Increased Sweating
Beyond blood sugar fluctuations and general autonomic nerve damage, several other factors can trigger unusual or excessive sweating in a person with diabetes. One distinct form is gustatory sweating, which is characterized by profuse perspiration on the face, scalp, and neck that occurs during or immediately after eating. This reaction is often a specific manifestation of autonomic neuropathy, particularly affecting the nerves around the salivary glands.
Gustatory sweating can be triggered by a wide range of foods, not just spicy items, and is essentially a misdirected signal from damaged nerves. Instead of signaling the salivary glands, the damaged nerves incorrectly stimulate the nearby sweat glands on the face and head.
Certain medications used to manage diabetes can also list excessive sweating as a known side effect. Specifically, drugs that stimulate the pancreas to produce more insulin, such as sulfonylureas like glipizide and glyburide, can sometimes cause sweating. This is frequently related to the medication over-lowering blood sugar, which then triggers the familiar hypoglycemic response.
The presence of an infection or fever, which is more common in individuals with poorly controlled diabetes, will naturally lead to increased sweating. The body’s immune response to an infection raises the core temperature, and the subsequent sweating is a normal physiological attempt to cool the body down. While not unique to diabetes, a new pattern of night sweats or fever-related perspiration should prompt an evaluation for an underlying illness.