Will Phentermine Show Up In A Blood Test?

Posted on Thu, 3 Apr 2014

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Thu, 3 Apr 2014 Answered on

Wed, 30 Apr 2014 Last reviewed on

Question : I took a prescribed phentermine 37.5 24 hours prior to a drug screen at my pain management Dr. office. I had not been using this prescription that I got in Sept. 2013 because of prescribed pain meds and while taking a break from the pain meds I took 1 phentermine and wonder if it will show on the drug screen? I also take 10mg.Amiloride 2x daily and would that flush the phentermine from my system.

Answered by Dr. Dr. Michelle Gibson (37 minutes later)

Brief Answer: may cause a false positive test for phentermine Detailed Answer: HI, thanks for using healthcare magic Yes, it is possible that it would show up. Because it is similar to amphetamines, it can potentially cause a false positive result for amphetamines. It is potentially detectable for 48 to 72 hours after it is used. The amiloride, a diuretic, would cause your urine to be dilute and could potentially decrease the chance that it would be picked up. It would not flush it but dilute your urine. If it is positive then it would be a false positive, since you are not actually using amphetamines. Your employer can ask for a more sensitive test (GC-MS, this stands for gas chromatography -mass spectrometry), this would be able to determine accurately that the test is not truly positive for amphetamines. This test can be done to check the accuracy of the screening test. I hope this helps, feel free to ask any other questions

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Dr. Michelle Gibson (13 minutes later)

This test is a required screening because my pain management Dr. is required by law to screen patients on long term pain management. I had not been taking my narcotic meds for the last 3 months so I felt it was ok to take the phentermine. I will never mix the meds and the phentermine was I pill in the last month. I forgot until after I had been the Dr. that I had taken the phentermine the day prior. I think my test will be okay and I can discuss this with him in 3 months when I see him again. I think if the there was a problem from the test in office he would have contacted me. They do the initial test in office and then ship it off to a lab for more extensive test. Do you think it is possible that the test didn't test positive for phentermine.

Answered by Dr. Dr. Michelle Gibson (2 minutes later)

Brief Answer: may be normal Detailed Answer: HI It may be ok and your doctor would know that you were given phentermine. Even if positive, it would be a false positive test that can easily be verified. Please feel free to ask any thing else

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Dr. Michelle Gibson (44 minutes later)

I appreciate the answers but called my Dr.'s office a few minutes ago and told them about my XXXXXXX taken the phentermine the day before. I want my medical providers to be completely informed about all my prescriptions and OTC's so I don't hinder their ability to provide the safest and most effective medical care for me. I sometimes forget or get side tracked when I go to an appointment as I did yesterday. Thank you for your responding to my questions. I should have saved my money and your valuable time and just called the Dr's office this morning when I hadn't received a call back from my message I left on their answering machine, stating I needed to discuss my RX's. Unfortunately my soliciting medical advice and answers from the web site does not serve my needs due to the nature of the vagueness and incomplete answers available.

Answered by Dr. Dr. Michelle Gibson (6 hours later)

Brief Answer: right course of action Detailed Answer: HI I agree with you about informing your doctor about the use of phentermine. It was the appropriate action. Wish you the best

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar