Feeling shaky usually comes down to your nervous system releasing stress hormones, your muscles running low on fuel, or a stimulant pushing your body into overdrive. Most causes are temporary and harmless, like too much coffee or not eating for several hours. But persistent or worsening shakiness can point to something worth investigating, from low blood sugar to medication side effects to mineral deficiencies.
Low Blood Sugar Is the Most Common Culprit
When your blood sugar drops below about 70 mg/dL, your body triggers an adrenaline response. That surge of epinephrine and norepinephrine is your body’s emergency system kicking in to raise glucose levels, and it produces a very recognizable set of symptoms: trembling hands, sweating, a pounding heartbeat, and a jittery anxiety that can feel like panic. You don’t need to have diabetes for this to happen. Skipping meals, exercising on an empty stomach, or drinking alcohol without eating can all pull your blood sugar low enough to set off this alarm.
If the drop is mild (between 54 and 70 mg/dL), you’ll typically feel shaky and hungry but can fix it quickly by eating something with fast-acting carbohydrates, like juice, fruit, or crackers. Below 54 mg/dL, your brain starts losing its primary fuel source, and symptoms shift from shakiness to confusion, difficulty concentrating, and impaired coordination. If you notice that shakiness reliably hits at certain times of day, especially mid-morning or late afternoon, the pattern itself is a strong clue that blood sugar is involved.
Caffeine and Stimulants
Caffeine is a central nervous system stimulant, and at high enough doses it directly causes tremors. Most adults start to feel jittery somewhere around 400 milligrams, roughly the amount in four standard cups of coffee, though individual tolerance varies widely. If you’re sensitive to caffeine or you’ve recently increased your intake, you can feel shaky at much lower amounts. Energy drinks, pre-workout supplements, certain teas, and even some medications contain caffeine that adds up faster than people realize.
Other stimulants produce the same effect. Amphetamines (including some ADHD medications), nicotine, and the decongestant pseudoephedrine all increase nervous system activity and can leave your hands trembling. The shakiness typically fades as the substance clears your system.
Anxiety and the Stress Response
Anxiety produces shakiness through the exact same mechanism as low blood sugar: an adrenaline surge. Your body can’t tell the difference between a real physical threat and a stressful email from your boss. Either way, it floods your system with epinephrine, which tenses your muscles, speeds your heart rate, and makes your hands tremble. During a panic attack, this response hits hard and fast, and the shakiness can be intense enough that people mistake it for a medical emergency.
Chronic stress keeps your baseline adrenaline elevated, so you may feel a low-level tremor or internal vibration throughout the day without any obvious trigger. If your shakiness comes with racing thoughts, chest tightness, or a sense of dread, your nervous system’s stress response is the likely explanation.
Muscle Fatigue After Exercise
If your legs shake after a long run or your arms tremble after lifting weights, that’s your neuromuscular system running out of its ability to coordinate smoothly. During sustained or intense effort, your brain compensates for tiring muscle fibers by recruiting larger motor units and increasing the firing rate of the nerves controlling those muscles. Eventually, this compensation breaks down. The motor units start firing out of sync, and the result is visible trembling.
This type of shakiness is completely normal and resolves on its own as your muscles recover, usually within 30 minutes to an hour. Eating a meal with protein and carbohydrates speeds recovery. If post-exercise shakiness is severe or lasts much longer, dehydration or low blood sugar during the workout may be amplifying the effect.
Medications That Cause Shakiness
A surprisingly long list of common medications can cause tremors as a side effect. The ones most frequently responsible include:
- Antidepressants: SSRIs and tricyclic antidepressants
- Asthma inhalers: albuterol and theophylline
- Mood stabilizers: lithium
- Seizure medications: valproate (Depakote)
- Thyroid medication: too high a dose of levothyroxine
- Steroids: both oral and inhaled corticosteroids
- Heart medications: amiodarone and similar drugs
- Immune-suppressing drugs: cyclosporine and tacrolimus
If you started a new medication recently and the shakiness followed, that timing is significant. Drug-induced tremors typically appear within weeks of starting a medication or increasing a dose, and they resolve when the medication is adjusted. Don’t stop any prescription medication on your own, but the timing is worth bringing up with whoever prescribed it.
Low Magnesium and Other Mineral Deficiencies
Magnesium plays a central role in nerve conduction and muscle function. When levels drop too low, your neuromuscular system becomes overly excitable, producing tremors, muscle spasms, cramping, and sometimes numbness or tingling in the hands and feet. Low magnesium rarely travels alone. It tends to drag calcium and potassium levels down with it, which compounds the shakiness.
Common causes of low magnesium include chronic alcohol use, prolonged diarrhea or vomiting, certain medications (especially diuretics and proton pump inhibitors), and diets consistently low in leafy greens, nuts, and whole grains. A simple blood test can identify the deficiency, though magnesium levels in the blood don’t always reflect what’s stored in your cells, so the test isn’t perfect.
Alcohol Withdrawal
If you drink heavily and regularly, your nervous system adapts to alcohol’s sedating effects by staying in a heightened state. When you suddenly stop drinking or significantly cut back, that heightened state has nothing to counterbalance it, and tremors are one of the earliest signs. The shakes typically begin within 6 to 24 hours after the last drink, often starting in the hands and progressing from there. Mild tremors can resolve on their own, but alcohol withdrawal can also escalate into a serious medical situation with seizures and severe confusion. The severity depends on how much and how long you’ve been drinking.
Thyroid Problems
An overactive thyroid (hyperthyroidism) speeds up nearly every system in your body. Your metabolism runs hot, your heart beats faster, and your nervous system becomes overstimulated. Fine tremors in the fingers and hands are a hallmark symptom, often accompanied by unintentional weight loss, heat intolerance, and difficulty sleeping. If shakiness comes with any of these, a thyroid panel blood test can confirm or rule it out quickly.
When Shakiness Points to Something Neurological
Most shakiness has a clear, reversible cause. But tremors that persist for weeks or months without an obvious explanation may involve the nervous system itself. The two most common neurological causes are essential tremor and Parkinson’s disease, and they behave differently in ways that are easy to observe.
Essential tremor shows up when you’re actively using your hands, like writing, eating with a fork, or holding a cup. It tends to run in families and often starts mild, gradually worsening over years. Parkinson’s tremor, by contrast, is most noticeable when your hand is at rest, like sitting in your lap, and decreases when you reach for something. Research using motion sensors confirms this distinction: in Parkinson’s patients, tremor intensity increases when the hand hangs relaxed, while in essential tremor patients, the opposite happens. Parkinson’s tremor also typically starts on one side of the body and comes alongside slowness of movement and stiffness.
Essential tremor is far more common than Parkinson’s and, while annoying, isn’t dangerous. Both conditions are manageable with treatment. If you’re noticing a progressive tremor that doesn’t line up with any of the other causes on this list, a neurologist can distinguish between them with a physical exam.