How Long Does Phentermine Stay in Your Urine?

Understanding Phentermine

Phentermine is a diet pill used to decrease appetite 12. Sometimes doctors prescribe the drug to treat obesity. The drug has been known to promote effective weight loss by creating a feeling of fullness. Use of this drug is recommended for short-term weight management only, as it gradually becomes less effective. An appetite suppressant, Phentermine helps an individual to control eating by blocking hunger messages to the brain 12. The drug also accelerates metabolism by burning calories at a faster rate. Usually following about six weeks of use, the body becomes resistant to the drug and adverse reactions begin to set in.

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Although not an amphetamine, Phentermine is a stimulant similar in chemical makeup to an amphetamine; therefore, the drug affects the body in much the same way 12. Taking the diet pill can cause a positive result in urine screening testing for amphetamines 3. Phentermine may be detected in the urine for up to two to four days, depending on how quickly the body metabolizes the drug 12. The rate varies among individuals and can be influenced by several factors including a person’s age, height, weight and amount of body fat. How much of the drug you take as well as how frequently you take it also determine how long it can remain in your system. In most cases, the drug cannot be detected in urine after 48 to 72 hours, but like other stimulants, Phentermine may still be detected for up to four days 12. Generally, the liver and kidneys clear most medications out of the body fairly quickly. However, in some cases, trace levels of a drug may remain in the system for a long time. In addition,, the weight loss site and network for Phentermine forums, points out that while the drug is FDA approved for weight loss, to date there have been few studies examining the long-term use of the appetite suppressant (see Reference 1) 12. Likewise, there is no clinical data available that measures the length of time Phentermine remains in the body after a person stops using the drug 12. Consuming caffeine may decrease the effects of the drug more quickly. Be advised that if your employer requires periodic drug testing, having Phentermine in your system may make it look as if you are taking amphetamines 123.


In addition to the numerous adverse physical effects extended or overuse of the drug can cause, because it affects the body’s nervous system in much the same way as amphetamines, Phentermine can be habit-forming 123. Like other stimulants, the drug elevates blood pressure and increases heart rate. Withdrawal symptoms may occur if you stop taking the diet pills abruptly. Talk to your doctor first before you stop this medication. He will give you instructions for gradually reducing the dosage. Do not increase dosage or take the drug for longer than recommended by your physician. Depression, irritability and fatigue are common side effects following withdrawal. Tell your doctor if you have increased hunger, swelling or rapid weight gain while taking the drug. Alcohol can increase the intensity of certain side effects.