Shakiness most often comes from something your body is doing right now, not a deeper neurological problem. Low blood sugar, too much caffeine, muscle fatigue, stress, poor sleep, or a medication side effect are the most common reasons otherwise healthy people suddenly feel shaky. Less commonly, persistent or worsening shakiness points to a condition that needs medical attention. Here’s how to figure out what’s going on.
Low Blood Sugar
When blood glucose drops below about 70 mg/dL, your body releases a burst of adrenaline to signal that it needs fuel. That adrenaline surge is what makes your hands tremble, your heart race, and your body feel jittery. You don’t need to have diabetes for this to happen. Skipping meals, eating mostly simple carbs, exercising on an empty stomach, or drinking alcohol without food can all pull your blood sugar low enough to trigger shakiness.
The fix is straightforward: eat something with both fast-acting sugar and a protein or fat to keep levels stable. If you notice that shakiness regularly hits a few hours after meals or in the mid-afternoon, the pattern itself is a clue that your blood sugar is swinging too far between meals. Eating more regularly and including protein at each meal usually resolves it.
Caffeine and Stimulants
Caffeine blocks a calming chemical in your brain and revs up your nervous system. While formal testing has shown that a single 325 mg dose (roughly a large coffee) doesn’t reliably produce tremor in most people, individual sensitivity varies enormously. If you’re sleep-deprived, anxious, or haven’t eaten, even a moderate amount of caffeine can push your nervous system past the threshold where your hands start to shake. Energy drinks, pre-workout supplements, and some cold medications stack stimulants in ways that amplify this effect.
If caffeine is the culprit, the shakiness typically resolves within a few hours as the stimulant clears your system. Cutting back gradually rather than quitting cold turkey helps you avoid withdrawal headaches.
Anxiety and Stress
Your body’s fight-or-flight response floods your muscles with adrenaline and cortisol, preparing you to move fast. When you’re sitting at your desk instead of running from danger, that chemical surge has nowhere to go, and the result is visible trembling, especially in your hands, legs, or voice. Chronic stress keeps this system partially activated for hours or days, which is why some people feel shaky even when they can’t point to a specific stressful event.
Shallow, rapid breathing makes this worse by shifting the balance of carbon dioxide in your blood, which increases nerve excitability throughout your body. Slow, deliberate breathing (in for four counts, out for six) directly counteracts this cycle. Regular physical activity helps burn off the excess stress hormones that keep your muscles on edge.
Muscle Fatigue
If your legs shake during a wall sit or your arms tremble while carrying groceries, that’s a normal response to tired muscles. During sustained effort, individual muscle fibers begin to fatigue and drop out, forcing your nervous system to recruit other fibers in a less coordinated pattern. Research on motor unit firing shows that as muscles fatigue, the force they produce becomes increasingly unsteady, and you feel that instability as visible shaking.
This type of tremor stops once you rest the muscle. It’s more noticeable when you’re new to exercise or when you push a muscle group harder than usual. It’s not a sign of damage.
Medication Side Effects
A surprisingly long list of common medications can cause shakiness. Antidepressants (particularly SSRIs), asthma inhalers containing albuterol, lithium, certain seizure medications, steroids, some antibiotics, and thyroid hormone replacement at too high a dose are all known to cause tremor. Stimulant medications for ADHD can do the same.
Drug-induced tremor typically starts within days to weeks of beginning a new medication or increasing a dose. If the timing lines up, bring it up with your prescriber. In many cases, adjusting the dose or switching to an alternative resolves the problem. Don’t stop a prescribed medication on your own.
Alcohol Withdrawal
If you drink heavily and recently cut back or stopped, shakiness is one of the earliest withdrawal symptoms. Tremors typically begin within 6 to 24 hours of your last drink, peak between 24 and 72 hours, and gradually ease after that. The shaking usually affects the hands first and can spread to other parts of the body.
Severe withdrawal can progress to seizures (highest risk at 24 to 48 hours) and delirium tremens (48 to 72 hours), both of which are medical emergencies. If you’re experiencing withdrawal tremors along with confusion, hallucinations, a racing heart, or fever, that combination requires immediate medical care.
Nutritional Deficiencies
Vitamin B12 plays a critical role in maintaining the protective coating around your nerves. When levels drop low enough, the nervous system misfires in various ways: tremor, numbness, tingling, difficulty with balance, and even cognitive changes. B12 deficiency is more common in people over 50, vegans and vegetarians, and anyone with digestive conditions that impair absorption.
Magnesium deficiency can produce a similar picture. Magnesium helps regulate nerve signaling and muscle contraction, so when stores run low, muscles become hyperexcitable and twitchy. Chronic stress, heavy sweating, alcohol use, and certain medications (like proton pump inhibitors) all deplete magnesium. A blood test can check both levels, and supplementation or dietary changes usually improve symptoms over several weeks.
Sleep Deprivation
Even one night of poor sleep increases the excitability of your nervous system. Your brain becomes less efficient at filtering and dampening nerve signals, which can show up as hand tremors, eye twitches, or a general sense of jitteriness. Combine poor sleep with caffeine to compensate, and the effect gets worse. If you’ve been consistently sleeping fewer than six hours, shakiness may not resolve until you’ve had several nights of adequate rest.
When Shakiness Points to Something Bigger
Most shakiness from the causes above is temporary and improves once the trigger is addressed. Persistent tremor that doesn’t go away, or that gradually worsens over months, deserves a closer look.
Essential tremor is the most common movement disorder, affecting an estimated 1 in 25 adults over 40. It causes a rhythmic shaking (typically 5 to 8 cycles per second) that’s most noticeable when you’re using your hands: writing, eating, pouring a drink. It often runs in families and tends to worsen slowly over years. The key feature is that the tremor appears during movement, not at rest.
Parkinson’s disease produces a slower tremor (4 to 6 cycles per second) that shows up when your hand is resting in your lap and typically stops when you reach for something. It usually starts on one side of the body and is accompanied by stiffness, slowness of movement, and changes in balance. A tremor that fits this pattern, especially alongside those other symptoms, warrants a neurological evaluation.
An overactive thyroid is another common medical cause of shakiness. It speeds up your metabolism across the board, producing tremor along with weight loss, a rapid heartbeat, heat intolerance, and difficulty sleeping. A simple blood test can confirm or rule it out.
If your shakiness is new, getting worse, present on only one side, or accompanied by other neurological changes like difficulty walking, slurred speech, or muscle weakness, those details help a doctor narrow down the cause efficiently.