The involuntary shaking that occurs while intoxicated or during a hangover, often called the “shakes” or “jitters,” is a common physiological reaction to the presence and then absence of alcohol in the body. These tremors signal that the central nervous system is struggling to maintain its delicate chemical balance. Understanding the underlying mechanisms—from the immediate depressant effects of alcohol to the later rebound hyperexcitability—provides insight into why this symptom occurs.
How Alcohol Affects Motor Control During Intoxication
Alcohol is classified as a central nervous system (CNS) depressant, meaning it slows down brain activity by interfering with the chemical messengers that nerve cells use to communicate. This immediate effect on the CNS causes acute shaking while a person is actively drinking. Alcohol significantly amplifies the effects of gamma-aminobutyric acid (GABA), the brain’s primary inhibitory neurotransmitter, essentially boosting the brain’s “off switch.”
Simultaneously, alcohol suppresses the activity of glutamate, the main excitatory neurotransmitter. This double-hit—increasing the inhibitory signal while decreasing the excitatory signal—disrupts the communication pathways that control muscle coordination. When signals to the muscles become scrambled, the result is impaired coordination and the acute motor instability that presents as shaking.
The Rebound Effect and Post-Intoxication Tremors
The shaking most people experience the morning after drinking is a delayed reaction caused by CNS hyperexcitability. To compensate for the constant suppression caused by alcohol, the brain adapts by reducing its sensitivity to GABA and increasing the production and sensitivity of glutamate.
Once alcohol is metabolized and leaves the system, these compensatory mechanisms are left unchecked. The upregulated excitatory glutamate system fires excessively without the calming effect of GABA. This chemical over-correction results in a mild, temporary withdrawal state, which manifests as the characteristic jitteriness, anxiety, and tremors of a hangover. These early withdrawal tremors typically begin six to twelve hours after the last drink and are often most noticeable in the hands.
Physical States That Worsen Shaking
Common physical side effects of alcohol consumption can intensify the severity of tremors. Alcohol acts as a diuretic, causing the kidneys to excrete more fluid than normal, which quickly leads to dehydration and an imbalance of electrolytes. Depletion of electrolytes like potassium and magnesium, which are necessary for proper nerve signaling, can directly contribute to muscle spasms and increased shakiness.
Hypoglycemia, or low blood sugar, is another major contributing factor. Alcohol interferes with the liver’s ability to regulate glucose levels because the liver prioritizes metabolizing alcohol over releasing stored glucose. This drop in blood sugar deprives the brain of its primary fuel source, resulting in symptoms like weakness, fatigue, and a noticeable increase in tremors.
When Shaking Signals a Medical Emergency
While mild shaking is a common part of a hangover, certain symptoms indicate a severe reaction requiring immediate medical attention. Shaking that becomes violent, persistent, or spreads to the entire body can be a sign of severe alcohol withdrawal. Tremors that begin six to twelve hours after the last drink are considered early withdrawal, but the most severe symptoms usually peak between 48 and 72 hours.
A medical emergency is signaled if the shaking is accompanied by hallucinations, confusion, fever, or seizures. This progression can indicate the onset of delirium tremens (DTs), a life-threatening form of alcohol withdrawal. Any sign of confusion, inability to hold down fluids, or an irregular heart rate along with severe tremors demands an immediate visit to an emergency room.