If you’re researching any drug or medicine it’s important to find reliable sources. One way you can check someone’s information is to follow their citations. If someone quotes a number (“1 in 5 people”) check to see if they’re linking that to any other page.
In the case of Phentermine, the popular weight loss drug used by over 3 million people in 202, there is a lot of misinformation out there, especially about side effects. In this article, I’ll show several articles and studies with safety data on Phentermine, with tiredness and fatigue listed as only mild or even non-reported symptoms.
Why Some Sources Say…
On the internet, some articles tend to cite one another without anyone going back to check the facts. One popular Phentermine website mentioned that “1 in 5” phentermine users reported fatigue or tiredness in some way. But when you click on the authors hyperlink–it goes to “Page Not Found.” There’s no study linked.
In fact, when researching this article, I could find no claims of major fatigue linked to any empirical data, study, or trial.
What Evidence Was Found?
I have found a national library of medicine source and a toxicology library listing side effects of phentermine, one study comparing withdrawal side effects, a prescription drug database, and an internationally recognized hospital source. Only one listed fatigue or tiredness as a possible side effect, and all instances were related to outside medical conditions.
Many, if not all, of the sources did list insomnia as a major side effect, which is a sleep cycle disruption whose ancillary effects many could confuse with tiredness or fatigue. The insomnia caused by phentermine is related to its stimulant effects.
As for the underlying conditions listed by the hospital site, these include potassium deficiency, interaction with seizure medications, skin conditions like Stevens-Johnson syndrome, and a serious condition called hyperammonemic encephalopathy, or excess ammonia in the brain.
What it All Means
The bottom line is that phentermine, in and of itself, does not cause tiredness or fatigue. If you do experience these symptoms, it is a sign of a serious medical event which requires immediate attention. It means there is some underlying condition or interaction which the phentermine use is exposing.
Anyone considering phentermine use should consult their primary care physician, who would know their medical history and suitability best.