Persistent shaking has dozens of possible causes, ranging from too much caffeine to a neurological condition like essential tremor. The most common culprit in otherwise healthy people is essential tremor, which affects roughly 1% of the general population and about 5% of adults over 60. But shaking can also be driven by low blood sugar, an overactive thyroid, anxiety, medication side effects, or substance withdrawal. Understanding the pattern of your shaking, when it happens, and what makes it better or worse is the fastest way to narrow down what’s going on.
Essential Tremor: The Most Common Cause
Essential tremor is the single most common cause of action tremor, meaning shaking that shows up when you’re actively using your hands or holding them in a position against gravity. You might notice it while writing, eating with a spoon, pouring a drink, or holding your phone up to your ear. It typically affects both hands and may also involve your head or voice. The shaking tends to get worse with fatigue, stress, caffeine, and temperature extremes.
Essential tremor often runs in families and can appear at any age, though it becomes more common as you get older. Over time, the strength of the tremor may increase even as the speed of the oscillation slows down. The amplitude can vary by as much as 23% throughout the day, which is why your hands might seem steadier in the morning and shakier by evening. If the tremor is mild, many people never seek treatment. When it starts interfering with daily tasks, a doctor can prescribe propranolol (a blood pressure medication) or primidone (an anti-seizure medication) as first-line options.
How Parkinson’s Tremor Looks Different
Parkinson’s disease produces a resting tremor, which is the opposite pattern from essential tremor. Your hand shakes when it’s relaxed in your lap or hanging at your side, and the shaking often stops or decreases when you reach for something. Parkinson’s tremor also typically starts on one side of the body before eventually spreading to both sides. If your shaking fits this description, especially if you’ve also noticed stiffness, slowness of movement, or changes in your walking, that’s a pattern worth bringing to a neurologist. A special brain scan that tracks dopamine activity can help distinguish Parkinson’s from essential tremor when the clinical picture is unclear.
Low Blood Sugar and Metabolic Triggers
If your shaking comes in episodes rather than being constant, low blood sugar is a likely suspect. When blood glucose drops below about 70 mg/dL, your body releases adrenaline to signal that it needs fuel. That adrenaline surge causes shakiness, sweating, a pounding heart, and irritability. People with diabetes experience this regularly, but it also happens to people without diabetes who skip meals, exercise intensely without eating, or drink alcohol on an empty stomach. The fix is straightforward: eating or drinking something with fast-acting sugar (juice, glucose tablets, a few crackers) usually resolves the shaking within 10 to 15 minutes.
Thyroid Problems
An overactive thyroid gland (hyperthyroidism) speeds up your entire metabolism, and one of the hallmark signs is a fine, fast tremor in your hands and fingers. Unlike essential tremor, which tends to be more visible and rhythmic, a thyroid-related tremor is often subtle, almost like a vibration you can see when you hold your hands out flat. You’d typically also have other symptoms: unexplained weight loss, a rapid or irregular heartbeat, heat intolerance, trouble sleeping, or feeling wired and jittery. A simple blood test measuring thyroid hormone levels can confirm or rule this out quickly. Taking too much thyroid replacement medication (levothyroxine) can produce the same effect.
Anxiety and Stress-Related Shaking
Your nervous system has a built-in alarm response that floods your body with adrenaline and cortisol when you feel threatened. That response causes shaking, a racing heart, shallow breathing, and muscle tension. For some people, chronic anxiety keeps this system activated at a low level throughout the day, producing a tremor that feels constant. Functional tremor, sometimes called psychogenic tremor, is a distinct neurological phenomenon where the shaking has real physical characteristics but is driven by the nervous system’s stress response rather than by a degenerative disease. It tends to come on suddenly, change in speed or location, and get better when you’re mentally distracted by a task. A neurologist can identify it by asking you to tap a rhythm with your unaffected hand. If the tremor in your other hand shifts to match that tapping rhythm, that’s a strong indicator of a functional tremor.
Medications That Cause Shaking
A surprisingly long list of common medications can cause tremor as a side effect. Some of the most frequent offenders include:
- Antidepressants (SSRIs and tricyclics)
- Mood stabilizers like lithium
- Asthma inhalers containing albuterol
- Stimulants including caffeine and medications for ADHD
- Anti-seizure medications like valproic acid
- Steroids
- Certain heart medications like amiodarone
- Immune-suppressing drugs used after organ transplants
If your shaking started or worsened after beginning a new medication, that timing is important information for your doctor. Drug-induced tremor usually improves once the medication is adjusted or switched, though it sometimes takes weeks to fully resolve.
Caffeine, Alcohol, and Substance Withdrawal
Caffeine is the most overlooked cause of shaking. It’s a central nervous system stimulant, and at high enough doses it produces a fine, fast tremor along with jitteriness and a rapid heartbeat. If you’re drinking more than two or three cups of coffee a day (or combining coffee with energy drinks, pre-workout supplements, or tea), try cutting back and see if the shaking improves.
Alcohol withdrawal is a more serious cause of tremor. Mild withdrawal symptoms, including shakiness, headache, and anxiety, typically begin within 6 to 24 hours after your last drink. For heavy, long-term drinkers, symptoms can escalate. Delirium tremens, the most severe form of alcohol withdrawal, can appear 48 to 72 hours after the last drink and involves intense shaking, confusion, fever, and hallucinations. This is a medical emergency. Even milder alcohol withdrawal tremors deserve medical supervision because the condition can worsen unpredictably. Nicotine withdrawal can also produce tremor, though it’s typically less intense.
What a Doctor Will Check
When you see a doctor for persistent shaking, the evaluation is largely hands-on. A neurological exam tests your reflexes, muscle strength, coordination, posture, and walking. To evaluate the tremor itself, you’ll likely be asked to hold your arms out straight, drink from a glass, write a sentence, and draw a spiral. The spiral test is particularly useful because it creates a visual record of your tremor’s severity and pattern that can be compared over time.
Blood tests typically check thyroid function, blood sugar, and basic metabolic markers. Your medication list and caffeine intake will be reviewed. If there’s any question about whether the tremor could be Parkinson’s disease, a dopamine transporter scan can show whether the brain’s dopamine-producing pathways are functioning normally. In most cases, though, a thorough physical exam and medical history are enough to identify the cause without advanced imaging.