Hand Tremor: Clinical Criteria That Distinguish Essential Tremor from Parkinson's Disease

Last updated: 2026-09-10

When a hand shakes, essential tremor and Parkinson's disease are distinguished by the situations in which the tremor appears and by any accompanying changes in movement. If both hands shake while the arms are held out in a fixed posture or while bringing a cup to the mouth, essential tremor is more likely. If one hand shakes while resting comfortably on the knee, along with slowed movement and muscle stiffness, parkinsonism is considered instead.

Tremor is classified by the situation in which it occurs — resting tremor versus action tremor — and international classification systems start the diagnostic process with this distinction¹. However, the two patterns can overlap in the same person, so a diagnosis is never made based on the triggering situation alone. During the clinical exam, doctors look for other movement symptoms besides the tremor itself to determine the likely direction.

What Does the Doctor Compare During the Exam?

The doctor compares the hand at rest, the arms held out in a sustained posture, and the hand performing a movement such as touching a finger to the nose. Which state causes the tremor to worsen helps determine what to check next.

Next, the patient is asked to tap their fingers rapidly and repeatedly, and the doctor observes whether the movement slows down or becomes smaller in amplitude over time. This change corresponds to bradykinesia (slowness of movement), a hallmark of parkinsonism. The doctor also moves the elbow and wrist passively to check for muscle rigidity.

Gait is also assessed. If one arm swings less while walking, or if stride length shortens along with the tremor, parkinsonism becomes a concern². The size of the tremor alone does not distinguish between the two conditions, so the exam also looks for other movement symptoms beyond the tremor.

The combination of findings from the exam determines the next step. If only action tremor is present with no other movement symptoms, reducing factors that worsen the tremor comes first. If resting tremor appears together with bradykinesia or rigidity, the evaluation moves toward an assessment focused on parkinsonism.

Could a Medication Be Causing the Tremor?

Drug-induced tremor and drug-induced parkinsonism are actually not rare, so this possibility is checked first during the exam³. The key step is comparing when the tremor started with when a medication was started or its dose was increased.

Certain medications can trigger tremor, including antipsychotics, some gastrointestinal drugs, bronchodilators, and thyroid hormone medications. Drug-induced parkinsonism often improves after stopping or switching the causative medication, and it needs to be distinguished from tardive dyskinesia, which differs in pattern and course⁴.

Bringing your prescriptions or a list of medications you're taking can speed up the visit. Do not stop any medication on your own — instead, inform the prescribing provider that a tremor has developed, and work together to decide whether to adjust the dose or timing.

When Are Additional Tests Needed?

Not every patient with tremor needs the same tests. Testing is decided based on questions that remain unanswered after the history and neurological exam.

If symptoms such as palpitations, weight loss, or heat intolerance are also present, thyroid function testing may be recommended. Overactive thyroid function can worsen action tremor, so this is checked when identifying the underlying cause.

If tremor occurs along with changes in gait, balance, or cognition, or if symptoms are concentrated on one side of the body, further evaluation by a neurologist is recommended. Brain imaging or ultrasound tests are used selectively to confirm a hypothesis that has already been narrowed down through the clinical exam⁵.

What Happens Once a Diagnosis Is Made?

Once the underlying cause is identified, treatment is tailored to that cause. If caffeine intake or lack of sleep is worsening the tremor, reducing caffeine and improving sleep duration is recommended.

If a medication is suspected as the cause, the prescribing provider reviews the necessity of the drug and the timing of symptom onset to decide whether to change it. If essential tremor is diagnosed and it interferes with daily activities like handwriting or eating, starting medication may be discussed.

If findings consistent with parkinsonism are also confirmed, referral to a neurologist follows to determine the diagnosis and treatment direction. The timing of treatment is based on which specific movements have become difficult, not how large the tremor appears.

When Should You See a Doctor Right Away?

If you find yourself redoing your signature repeatedly, dropping food with chopsticks, or needing both hands to hold a cup of water, it's time to see a doctor. Even if the tremor looks small from the outside, if it's interfering with everyday movements, the underlying cause should be identified.

If tremor begins in only one hand along with slowed movement, or if one arm swings less while walking, don't wait and watch — seek medical care.

If a sudden tremor occurs together with weakness on one side of the body or slurred speech, don't wait for a regular outpatient appointment — use emergency medical services (such as calling 911) right away.

Frequently Asked Questions

If both hands shake, does that always mean essential tremor?

Tremor in both hands during sustained posture or movement is common in essential tremor, but this alone doesn't confirm the diagnosis. Resting tremor and action tremor can overlap in the same person, so the exam checks for other movement symptoms, such as bradykinesia and rigidity.

If the tremor is minor, can I put off seeing a doctor?

The decision isn't based on how large the tremor looks, but on how much it interferes with actual movements. If you're redoing your signature, dropping food with chopsticks, or needing both hands to hold a glass of water, the cause should be checked even if the tremor appears mild.

If I stop my medication, wouldn't that tell me if it's the cause?

Do not stop any medication on your own. Instead, compare when the tremor started with when the medication was started or the dose was increased, and have the prescribing provider review the necessity of the medication together with the timing of your symptoms to decide whether a change is needed.

If I have a hand tremor, do I definitely need a brain imaging test?

Not every patient with tremor needs the same test. Imaging or ultrasound tests are used selectively to confirm a hypothesis that has already been narrowed down through the history and physical exam.

In what situations should I use emergency medical services right away?

If a sudden tremor occurs together with weakness on one side of the body or slurred speech, don't wait for a regular outpatient appointment — use emergency medical services (such as calling 911) right away.

References

Medical Review: Dr. Joomin Kim, Director · The Wells Clinic Jamsil Main Branch