A tremor is an involuntary, rhythmic shaking movement in one or more parts of your body. It most commonly affects the hands, but it can also occur in the arms, head, jaw, legs, or voice. Tremors are caused by problems in the parts of the brain that control movement, though some degree of tremor is completely normal and happens to everyone.
Normal Tremor vs. Pathological Tremor
Everyone has a very slight tremor in their hands at all times. This is called physiological tremor, and it’s usually invisible to the naked eye. It becomes noticeable, or “enhanced,” when you’re stressed, anxious, fatigued, or have had too much caffeine. Low blood sugar and certain medications can also bring it out. Enhanced physiological tremor is temporary and goes away once the trigger does.
Pathological tremor is different. It’s persistent, often visible, and caused by an underlying neurological condition or other medical issue. This is the type that typically brings people to a doctor.
Resting vs. Action Tremors
The most important distinction doctors make is whether a tremor happens at rest or during movement.
Resting tremors appear when a body part is completely relaxed and supported, like when your hands are sitting in your lap. They tend to decrease or disappear when you start moving. The classic example is Parkinson’s disease tremor, which occurs at a slow rhythm of about 3 to 6 cycles per second. Around 90% of people with Parkinson’s have a resting tremor.
Action tremors are the opposite. They show up when you’re actively using a body part. These break down further into a few subtypes:
- Postural tremor: occurs when you hold a position against gravity, like stretching your arms out in front of you.
- Kinetic tremor: occurs during voluntary movement, such as lifting a glass to drink.
- Intention tremor: a specific type of kinetic tremor that gets worse as your hand approaches its target, like touching your finger to your nose.
Essential Tremor
Essential tremor is the most common pathological tremor in adults. It primarily produces action tremor, meaning the shaking shows up when you’re doing things with your hands: writing, eating, pouring a drink. It typically affects both sides of the body, though one side is usually worse than the other. The tremor frequency ranges from 4 to 12 cycles per second.
Beyond the hands, essential tremor can involve the head (a nodding or shaking motion) and the jaw. Head tremor in essential tremor is postural, meaning it disappears when you lie down. The condition tends to run in families and often gets slowly worse over years. It does not involve the slowness of movement (bradykinesia) that characterizes Parkinson’s disease.
Parkinsonian Tremor
Parkinson’s disease tremor looks and behaves differently from essential tremor. It’s primarily a resting tremor, often described as “pill-rolling” because it looks like someone rolling a small object between their thumb and fingers. It typically starts on one side of the body. When a person with Parkinson’s holds their arms outstretched, a tremor may re-emerge after a delay of several seconds, matching the same slow 4 to 6 cycle per second rhythm as the resting tremor.
Parkinson’s also comes with other movement changes that essential tremor does not: progressively smaller handwriting, slow movements, stiffness, and changes in walking and balance. The jaw tremor in Parkinson’s tends to happen when the mouth is closed and at rest, which is the reverse of the jaw tremor in essential tremor.
Other Causes of Tremor
Tremor isn’t always a primary neurological condition. It can be a symptom of something else entirely.
Hyperthyroidism (an overactive thyroid) causes tremor in roughly 76% of affected individuals. The tremor is typically a fast, fine shaking in both hands that resembles an exaggerated version of normal physiological tremor. It improves once thyroid levels are corrected. Damage to the cerebellum, the brain region responsible for coordination, causes a distinctive intention tremor. This type of damage can result from stroke, tumors, inherited conditions, or long-term heavy alcohol use.
Dystonia, a condition where the brain sends incorrect signals causing muscles to contract abnormally, can also produce tremor. Dystonic tremor tends to occur alongside unusual postures or sustained muscle contractions.
Medication-Related Tremor
A surprisingly long list of medications can cause tremor as a side effect. Common culprits include asthma inhalers (albuterol), mood stabilizers (lithium), certain antidepressants, seizure medications, immunosuppressants, some heart medications, stimulants, steroids, and even too much thyroid replacement medication. Alcohol, nicotine, and caffeine can also contribute. If a tremor starts shortly after beginning a new medication, the drug is a likely suspect.
How Tremor Is Evaluated
Doctors diagnose tremor primarily through observation and physical examination rather than lab tests. A neurological exam checks tendon reflexes, muscle strength and tone, coordination, posture, and balance. To evaluate the tremor specifically, you may be asked to hold your arms outstretched, drink from a glass, write your name, or draw a spiral. These tasks reveal whether the tremor is present at rest, during sustained posture, or during movement, which points toward the underlying cause.
Finger tapping tests help distinguish Parkinson’s from essential tremor. If tapping between your thumb and index finger becomes progressively smaller or freezes, that pattern suggests Parkinson’s. Pouring water from one cup to another is another useful test: worsening tremor during this task is typical of essential or dystonic tremor. When the diagnosis is still uncertain, a specialized brain scan can check dopamine activity, which is reduced in Parkinson’s but normal in essential tremor.
Treatment Options
Treatment depends entirely on the type of tremor and how much it affects daily life. Many people with mild tremor don’t need treatment at all.
For essential tremor, certain blood pressure and anti-seizure medications are first-line options that reduce shaking for many people. When medications don’t work well enough, two procedural options exist. Deep brain stimulation involves implanting small electrodes that send electrical signals to the thalamus, a deep brain structure involved in involuntary movement. This requires surgery but is adjustable and reversible.
A newer alternative is focused ultrasound, which earned FDA approval for essential tremor in 2016. It uses concentrated beams of ultrasound energy to precisely target a small area of the thalamus without any incision. Because it’s noninvasive, it appeals to people who want to avoid surgery. In late 2022, the FDA approved treating both sides of the brain with this technique, with at least nine months between treatments.
For Parkinson’s tremor, treatment focuses on the underlying disease itself. For drug-induced tremor, reducing or switching the offending medication often resolves the problem. For thyroid-related tremor, normalizing thyroid hormone levels is the fix.
Signs That Need Prompt Attention
A tremor that comes on suddenly, especially on one side of the body, could signal a stroke or other acute brain event. Tremor paired with significant difficulty walking, slowness of movement, muscle rigidity, or changes in speech warrants a neurological evaluation. The same applies if a tremor is getting progressively worse over weeks or months, interfering with eating, writing, or other daily tasks. A tremor that appears only at rest and diminishes with movement should be evaluated for Parkinson’s disease, particularly if it’s accompanied by smaller handwriting or shuffling steps.