Shakiness

People describe shakiness as an internal trembling with or without visible movement. It typically reflects sympathetic activation: adrenaline raises muscle spindle sensitivity and produces enhanced physiological tremor along with palpitations, sweating and anxiety. Reactive or fasting hypoglycaemia is the classic metabolic cause, and in people on insulin or sulfonylureas it is both common and dangerous. In people without diabetes, true hypoglycaemia is uncommon and needs documented low glucose during symptoms with relief on correction before it is accepted as the explanation. Other frequent drivers are caffeine, nicotine withdrawal, alcohol withdrawal, salbutamol and other beta-agonists, thyroid hormone excess, and anxiety states. Persistent visible tremor of the hands is a different entity — essential tremor or parkinsonism — and is assessed by whether it occurs at rest or with action.

• •Internal trembling or visible fine tremor
• •Palpitations
• •Sweating and pallor
• •Hunger and light-headedness
• •Anxiety or a sense of dread
• •Symptoms relieved by eating (suggests glucose)

• •Hypoglycaemia, especially on insulin or sulfonylureas
• •Caffeine and stimulant intake
• •Anxiety and panic attacks
• •Alcohol or benzodiazepine withdrawal
• •Hyperthyroidism
• •Beta-agonist inhalers
• •Enhanced physiological tremor

Catecholamine release, whatever the trigger, is the final common pathway. Hypoglycaemia, panic, stimulant intake and thyrotoxicosis all raise adrenergic tone. Alcohol and benzodiazepine withdrawal produce shakiness through loss of GABAergic inhibition, which is why the tremor is coarse and comes with autonomic instability.