The effects of Xanax depend on the dosage, but in general, you can expect to feel calmer within an hour. People who use Xanax heavily can build a tolerance to these effects as well as feelings of euphoria, which is why the drug is highly misused.

Xanax can cause side effects that often go away once your body gets used to the medication, including:

Serious side effects aren't very common, but if you experience any of the following symptoms call your doctor right away:

Drinking alcohol and/or using illicit drugs makes the chances of life-threatening side effects of Xanax higher.

Xanax bars is considered an short-acting benzodiazepine drug. After taking Xanax in pill form, peak levels are found in your blood 1 to 2 hours later. The average half-life of Xanax in the blood is 11.2 hours in healthy adults, meaning that half of the drug has been metabolized and eliminated in the urine in that time frame. It takes about five half-lives for 98% of a drug dose to clear the body, so Xanax takes two to four days to be fully eliminated from the body.

Xanax is detectable in your blood, urine, saliva, and hair, but how long it's detectable depends on a variety of individual factors.

Blood levels may be done as a screening test or in cases of treatment for a suspected overdose, but they can only detect if you've taken Xanax in the last 24 hours.

A urine drug screen, such as those that are done for employment, will test positive for benzodiazepines for five days and up to a week after a dose. For populations who metabolize Xanax more slowly—such as the elderly, obese, and those with alcoholic liver disease—that time maybe even longer.

Xanax can be detected in saliva for up to 2.5 days.1

As with all drugs, Xanax can be detected in your hair starting two to three weeks after and for up to 90 days after your last dose.

There are some medications that may cross-react with immunoassay urine drug screens. The antidepressant medication Zoloft (sertraline) and prescription non-steroidal anti-inflammatory drug Daypro (oxaprozin) can cause false-positive urine screens for benzodiazepines like Xanax.2

If you are taking Xanax by prescription and you have a drug screening or test, tell the testing laboratory so they can properly interpret your results. If you're being screened at work, you may want to let your employer know that you're taking Xanax ahead of time.

Your age, weight, body fat, other medications, dose, length of time taking Xanax, hydration level, and metabolism all affect how long it takes for the drug to be eliminated from your system. The half-life of Xanax tend to be longer for older adults, people of Asians descent, people with obesity, and those with liver disease.

Your age can play a factor in the half-life of Xanax. For example, the average half-life is roughly 11 hours in young, healthy adults compared to a little over 16 hours in healthy, senior adults. 

When you’re overweight, it’s more difficult for your body to break down Xanax, which can increase the half-life of the drug. 

Studies show that people of Asian descent take longer than Caucasians to excrete the drug from the body—the half-life of Xanax is approximately 15% to 25% higher in Asian people.

People with a higher metabolism, for example, those who are physically active, tend to be able to excrete Xanax faster. Hydration, age, and other health conditions may also play a role in a person's metabolic rate. 

Alcohol and Xanax is a dangerous duo that can lead to a fatal overdose. Alcohol can increase the effects of Xanax as well as the time it takes for the drug to leave your system. What's more, people with chronic liver disease due to years of alcohol use have a harder time breaking down the drug in their bodies, resulting in a half-life of nearly 20 hours versus 11.2 in healthy adults.

The concentration of Xanax in the blood is up to 50% less in smokers than non-smokers.

Because Xanax can create feelings of relaxation, calm, and well-being, and because it doesn't take long before your body builds a tolerance to the dose you're taking, it has the potential to be habit-forming. Your doctor will likely start you on the lowest dose possible to see if it's effective and aim to keep you on the lowest effective dose.

Take your prescription on the schedule and dosage your doctor prescribed. Do not cut or crush extended-relief pills as this gives you a larger dose all at once and may cause an overdose.

Symptoms of Xanax overdose can include:

Interactions with other medications can lead to serious, life-threatening breathing problems, sedation, and coma while you are taking Xanax. Discuss with your doctor all prescription and over-the-counter medications you're taking, plan to take, or plan to discontinue. Some medications of special concern are opiate medications such as codeine, hydrocodone, vicodin, hydromorphone, meperidine, methadone, morphine, oxycodone, and tramadol.

You may experience withdrawal symptoms if you suddenly stop taking Xanax. Don't stop or decrease your dose on your own as this can be dangerous, and can increase the risk of seizure. Talk to your doctor, who will prescribe an appropriate tapering schedule that will minimize or eliminate any potential physical or psychological symptoms of Xanax withdrawal.

Many people who are prescribed Xanax worry about becoming addicted to the drug. While Xanax is safe for most people when taken as advised, people with a history of alcohol or drug use disorders may be at greater risk.