Although taking phentermine typically produces the desired effects, it may also cause unwanted side effects such as serious heart or lung problems.
Consult your doctor immediately if you notice any of the following signs, which indicate a serious adverse reaction to phentermine:
There are other, more common side effects that may occur but do not usually require medical attention. They may be uncomfortable, but should go away during treatment as your body adjusts to the medicine. However, if these side effects persist or become more problematic, you should contact your doctor for advice.
The most common side effects include [1-4]:
These types of side effects do not usually require medical attention and although they may be uncomfortable, they should go away during treatment as your body adjusts to the medicine. However, if these side effects persist or become more problematic, you should contact your doctor.
The following data shows the most common side effects reported by phentermine users in a recent poll:
As you can see in the chart, xerostomia (dry mouth) is by far the most common side effect, as it is reported by over 73% of the respondents. Around half of respondents reported suffering from insomnia, and many have also reported other reactions such as headaches, constipation, dizziness, and rapid heartbeat.
There are additional potential side effects that have proven to be less common. Some of these are more serious than others, but you should contact your doctor if any of the following become chronic or problematic [1-5]:
Other side effects which are not listed above may also occur in some patients. If you notice any unusual, persistent or worsening side effects, inform your doctor immediately.
The following side effects may indicate a phentermine overdose [6]:
If you are worried about the possibility of suffering from any of these side effects, you might want to consider using an alternative to phentermine. Phentermine.com officially recommends Phen Caps, which is an efficient weight loss supplement that will help initiate your weight loss journey without the occurrence of side effects such as those listed above.
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1. Rueda-Clausen CF, Padwal RS, Sharma AM. New pharmacological approaches for obesity management. Nat Rev Endocrinol. 2013;9(8):467-478.
2. Velazquez A, Apovian CM. Updates on obesity pharmacotherapy. Ann N Y Acad Sci. 2018;1411(1):106-119.
3. Kim KK, Cho HJ, Kang HC, et al. Effects on weight reduction and safety of short-term phentermine administration in Korean obese people. Yonsei Med J. 2006;47(5):614-625.
4. Alexander J, Cheng YH, Choudhary J, Dinesh A. Phentermine (Duromine) precipitated psychosis. Aust N Z J Psychiatry. 2011;45(8):684-685.
5. Weintraub M, Hasday JD, Mushlin AI, Lockwood DH. A double-blind clinical trial in weight control. Use of fenfluramine and phentermine alone and in combination. Arch Intern Med. 1984;144(6):1143-1148.
6. Koury R, Stone CK, Stapczynski JS, Blake J. Sympathetic overactivity from fenfluramine-phentermine overdose. Eur J Emerg Med. 1999;6(2):149-152.
