Night tremors, the involuntary shaking or trembling that happens while you’re sleeping or trying to fall asleep, can stem from a wide range of causes. Some are temporary and harmless, like caffeine or stress. Others point to underlying conditions involving your nervous system, metabolism, or hormones. Understanding the most common triggers can help you figure out what’s going on and whether it needs attention.
How Tremors Happen at Night
Tremors are rhythmic, involuntary muscle contractions. During the day, your brain constantly fine-tunes muscle activity to keep your movements smooth. At night, when your body shifts into rest mode, certain imbalances become more noticeable. Your brain’s ability to suppress unwanted signals can weaken during lighter sleep stages, and conditions that cause tremors during the day often persist or even worsen at night when you’re lying still and more aware of subtle sensations in your body.
Some people experience visible shaking that a partner can see. Others describe what’s known as “internal tremor,” a buzzing or vibrating feeling inside the body with no visible movement. Internal tremors are surprisingly common: about 33% of people with Parkinson’s disease, 36% of people with multiple sclerosis, and 55% of people with essential tremor report experiencing them.
Anxiety and Stress
Anxiety is one of the most common reasons for nighttime trembling, especially in otherwise healthy people. When your body is in a prolonged state of stress, your adrenal glands release adrenaline and cortisol. These hormones prime your muscles for action, increasing tension and causing trembling or shaking even when you’re lying in bed. Elevated cortisol and adrenaline also make it harder for your body to relax enough to fall asleep, which creates a feedback loop: poor sleep raises anxiety, and anxiety disrupts sleep further.
Nocturnal panic attacks can also cause sudden trembling. These episodes strike during sleep, often in lighter sleep stages, and produce the same symptoms as daytime panic: shaking, rapid heartbeat, sweating, and a sense of dread. If your night tremors come on suddenly and are accompanied by a racing heart or shortness of breath, anxiety may be the primary driver.
Low Blood Sugar
When blood sugar drops below about 70 mg/dL, your body triggers an emergency response. Adrenaline floods your system to mobilize stored glucose, and one of the most recognizable side effects is shaking or trembling. This is especially common in people with diabetes who take insulin or certain oral medications, but it can also happen in people without diabetes after skipping meals, drinking alcohol on an empty stomach, or exercising heavily before bed.
Nighttime low blood sugar episodes are easy to miss because you’re asleep when they start. You might wake up shaking, drenched in sweat, or feeling disoriented. If this happens regularly, tracking your blood sugar before bed and having a small snack that includes protein and complex carbohydrates can help stabilize levels overnight.
Medications That Trigger Tremors
Several widely prescribed medications list tremor as a side effect. The most common culprits include antidepressants (both SSRIs and SNRIs), lithium, valproate (used for seizures and mood stabilization), certain heart rhythm drugs like amiodarone, and bronchodilators used for asthma. Stimulants, including prescription medications for ADHD as well as high caffeine intake, can also cause or worsen trembling at night.
Drug-induced tremors sometimes appear weeks or months after starting a medication, which makes the connection easy to overlook. If your tremors started or worsened around the time you began a new prescription, that timing is worth mentioning to your prescriber. In many cases, adjusting the dose or switching medications resolves the problem.
Alcohol Withdrawal
Alcohol suppresses your nervous system. With prolonged heavy use, your brain compensates by becoming more excitable to maintain balance. It dials down calming signals and ramps up stimulating ones. When you suddenly stop drinking or significantly cut back, that compensation is unmasked: your nervous system goes into overdrive.
Tremor is one of the earliest and most recognizable withdrawal symptoms, typically appearing within 6 hours of the last drink. It usually starts in the hands but can spread to the whole body. These early withdrawal symptoms, including tremor, insomnia, and restlessness, generally peak within the first 24 to 48 hours. Nighttime can feel particularly intense because there are fewer distractions and the body is attempting to rest while the nervous system is firing on all cylinders.
Neurological Conditions
Several neurological disorders cause tremors that persist or worsen at night.
Parkinson’s disease produces a characteristic resting tremor, typically at a frequency of 4 to 6 cycles per second, that’s most noticeable when the affected limb is relaxed and not actively moving. Lying in bed creates exactly these conditions. People with Parkinson’s often notice trembling in one hand or arm while trying to fall asleep or during nighttime awakenings. The tremor is just one piece of the picture, though. Slowness of movement, stiffness, and changes in balance are also hallmarks.
Essential tremor, the most common movement disorder, typically causes shaking during intentional movement (like reaching for a glass), but many people with essential tremor also experience internal tremors or visible shaking at rest, particularly as the condition progresses. Multiple sclerosis can produce tremors as well, caused by damage to the nerve pathways that coordinate muscle control.
Thyroid Problems
An overactive thyroid (hyperthyroidism) speeds up your metabolism and increases your body’s sensitivity to adrenaline. This heightened sensitivity leads to tremor, rapid heartbeat, weight loss, and difficulty sleeping. The tremor tends to be fine and fast, most noticeable in outstretched hands, and it doesn’t go away at night. If your night tremors are accompanied by unexplained weight loss, heat intolerance, or a racing pulse, thyroid function is worth investigating with a simple blood test.
Restless Legs vs. Night Tremors
Restless legs syndrome and periodic limb movement disorder are sometimes confused with night tremors, but they’re distinct conditions. Restless legs syndrome involves an irresistible urge to move your legs, usually accompanied by uncomfortable crawling, burning, or tugging sensations. It’s worst when you’re lying still and temporarily relieved by movement. Periodic limb movement disorder involves repetitive jerking or twitching of the legs or arms every 20 to 40 seconds during sleep. People with this condition are usually unaware of the movements, though a bed partner may notice them.
True tremors are rhythmic and continuous, while periodic limb movements are brief, repetitive jerks with pauses between them. The distinction matters because the causes and treatments are different. An overnight sleep study (polysomnography) can help sort this out. The test uses sensors to monitor brain activity, heart function, breathing, and limb movements while you sleep. Adults are diagnosed with periodic limb movement disorder when they have more than 15 limb movements per hour during the study.
Less Common Causes
Electrolyte imbalances, particularly low magnesium, calcium, or potassium, can increase nerve excitability and cause muscle tremors or twitching. These imbalances can result from dehydration, heavy sweating, certain diuretics, or digestive conditions that impair nutrient absorption.
Sleep deprivation itself can trigger tremors. When you’re severely sleep-deprived, your nervous system becomes more reactive, and fine motor control deteriorates. People who work night shifts or have chronic insomnia sometimes develop trembling that resolves once they catch up on rest.
High fever, particularly in the early stages of an infection, causes chills and shaking as your body tries to generate heat to raise its internal temperature. This type of shaking is usually obvious in context and resolves as the fever breaks.