What could be the cause of having hands shaking constantly?

Many: The differential diagnosis for tremor is quite large, i.e. there are many possible causes, ranging from too much caffeine, to anxiety, to a host of neurological disorders. See your primary care doctor and if he/she can't figure it out, ask for a referral to a neurologist.

??Family History: The most common reason for tremors at your age is Benign Familial Tremor....is what it sounds like a harmless family "problem"...You will need a detailed family history. If negative , a visit to a neurologist might be in order. Hope this helps Dr Z

Many different poss: At age 18, the most common causes would be too much caffeine, excess thyroid activity, or stimulants. Please see your doctor if it persists after reducing your caffeine intake.

Several causes: Causes of tremor(shaking)include: neurologic illnesses, hereditary disorders, substance abuse and substance withdrawal, over active thyroid gland, adrenalin producing tumor, nervousness, excess caffeine and a great many other causes. For a more detailed discussion, for patients, the NIH is a good start. Go to 1.usa.gov/1GkYldn