Xanax should only be taken with prescription and as directed by the physician. The maximum daily recommended dose of Xanax is 4 mg. given in divided dosage. However, age, medical condition and other factors are taken into consideration in determining the right dosage in using this medication. An overdose of this medication can lead to extreme drowsiness, confusion, loss of balance or coordination and fainting which can be lethal. Here's the link for more information: http://www.drugs.com/dosage/xanax.html.