Phentermine is a prescription medication that can affect each user in a different manner. Most users will experience nervousness or sleeplessness when first using Phentermine, but these side effects will lessen as you continue to take the medication.

Some Phentermine side effects do include mild notations such as an upset stomach, constipation or dry mouth or blurred vision. Most Phentermine users who do experience these side effects notice that they do lessen as they continue to take the medication. Not all users will experience all or any of these effects. Alcohol does increase the noticed side effects when using Phentermine.

Additional Phentermine users have noticed or experienced other side effects such as difficulty breathing, increased heart rates, severe dizziness, chest pains, and swelling from retaining water. If you experience these symptoms you may have allergies to Phentermine, you may have other underlying medical problems that Phentermine is making more noticeable and you should quit taking Phentermine and consult your family doctor for a complete physical.