A tremor is an involuntary, rhythmic movement of a body part, such as the hands, arms, head, or voice. This common movement disorder results from alternating contractions between opposing muscle groups. Understanding why your hands shake involves classifying the tremor based on when it occurs: either as a resting tremor, which happens when the muscle is relaxed, or as an action tremor, which occurs during voluntary muscle contraction. A chronic hand tremor warrants investigation, as the cause can range from temporary physiological factors to underlying neurological conditions.
Common Lifestyle and Metabolic Triggers
The most frequent cause of temporary hand shakiness is an enhancement of the body’s normal physiological tremor. This tremor is low in amplitude but becomes more noticeable under certain conditions. High intake of caffeine, a stimulant, triggers the nervous system and increases circulating levels of epinephrine (adrenaline). This surge of epinephrine over-stimulates the muscles, making the subtle natural tremor more pronounced.
Acute stress, anxiety, or fatigue can cause a temporary tremor by activating the “fight-or-flight” response, flooding the body with excitatory hormones. Low blood sugar (hypoglycemia) is another metabolic trigger that causes shakiness because the body releases adrenaline to signal the liver to produce more glucose. Addressing these causes involves simple lifestyle adjustments like reducing stimulant intake or managing stress, and the tremor typically subsides once the trigger is removed.
Essential Tremor
Essential Tremor (ET) is the most common neurological movement disorder, affecting millions, and is the likely culprit behind many chronic hand tremors. This condition is characterized by an action tremor, meaning the shaking is most apparent when the hands are actively being used or held in a fixed position against gravity. Activities like drinking from a glass, writing, or holding a newspaper typically provoke the tremor.
The tremor is generally bilateral, affecting both hands, and may also involve the head or voice. While not life-threatening, it can significantly interfere with daily activities. The condition often has a hereditary component, running in families, which is why it is sometimes referred to as familial tremor.
Medication Side Effects and Substance Use
Many tremors are iatrogenic, meaning they result directly from prescribed medications or substance use. Several common drug classes can induce or worsen a tremor by affecting the nervous system’s function. These include certain mood stabilizers like lithium, some antidepressants such as selective serotonin reuptake inhibitors (SSRIs), and a class of medications for asthma known as beta-agonists.
Other notable culprits include some seizure medications, corticosteroids, and excessive doses of thyroid hormone replacement therapy. In addition to prescription drugs, chronic heavy alcohol use can cause a persistent tremor, and abrupt cessation of alcohol can trigger a severe, temporary withdrawal tremor. Patients experiencing medication side effects should always consult their prescribing physician before making any changes to their regimen.
Underlying Neurological and Endocrine Conditions
A tremor can also be a sign of a more complex underlying health issue, including specific neurological and endocrine disorders. The tremor associated with Parkinson’s Disease (PD) is a resting tremor, most prominent when the hand is completely relaxed and supported, often described as a “pill-rolling” motion. This shaking usually starts asymmetrically, affecting one side of the body more than the other, and often lessens or disappears entirely during intentional movement.
Multiple Sclerosis (MS) can cause a different type of shaking called an intention tremor. This tremor develops and worsens as the hand moves closer to a target, such as reaching to touch a nose or pick up an object. Intention tremors in MS result from damage to the cerebellum, the part of the brain responsible for coordinating movement.
Separately, an overactive thyroid gland (hyperthyroidism) causes a fine, rapid, postural tremor. This results from the excessive production of thyroid hormones, which increase the overall metabolic rate and neuronal excitability.
When to Seek Professional Medical Guidance
While many tremors are minor and related to lifestyle factors, certain characteristics suggest the need for a professional medical evaluation. You should consult a doctor if the tremor has a sudden onset or if it is accompanied by other neurological symptoms like muscle stiffness, difficulty with balance, or slowness of movement. A medical professional should also be consulted if the tremor begins to significantly interfere with your ability to perform everyday tasks, such as writing, eating, or dressing.
A persistent tremor that occurs when your hands are fully at rest, or one that worsens progressively over weeks or months, warrants a medical evaluation. Only a doctor can determine the precise cause of the tremor and distinguish between benign conditions and those that require specific medical management. Discussing any tremor that impacts your quality of life is the first step toward finding appropriate management strategies.