Can I expect phentermine side effects?
Yes. Most people experience some phentermine side effects during the first few days or weeks after starting the medication. Most are mild and manageable, but it is important to understand what is normal and what may need a doctor’s attention.
Phentermine is a prescription medication that can be used short-term for weight loss. It works by affecting brain chemicals that help control hunger. Because of how it works, side effects are possible and can vary from person to person.
Why Does Phentermine Cause Side Effects?
Phentermine is a stimulant, similar to amphetamines. It increases certain signals in your brain that reduce appetite, but it can also cause:
- Heart rate may increase
- Blood pressure to rise
- Sleep patterns are to be disrupted
- Mood and energy levels to shift
The Mayo Clinic explains that the stimulant effect of phentermine is why common side effects like insomnia, nervousness, and increased heart rate can happen.
Common Phentermine Side Effects
The most common phentermine side effects that people report are mild and usually improve as your body adjusts to the medication. These side effects vary by person and normally depend on your dose, when you take your medication, and how your body responds.
These are the most commonly reported phentermine side effects:
- Dry mouth
- Constipation
- Insomnia
- Jitters or restlessness
- Mild to moderate headaches
Less Common Phentermine Side Effects
Some phentermine side effects happen less often and are not as well known, but it is important to understand them and be aware that they can happen.
Less common phentermine side effects may include:
- Experiencing unpredictable mood swings
- Irritability or having a short temper
- A decrease in your sex drive
- Feeling dizzy or lightheaded
Serious Phentermine Side Effects
Some symptoms are not normal and should be taken seriously. If you notice any of the signs below, contact your doctor right away or seek urgent care.
Some red flags to watch for when using phentermine:
- Chest pain, fainting, shortness of breath, or swelling in your legs.
- Severe headache, vision changes, or symptoms of very high blood pressure.
- Severe agitation, hallucinations, or unusual thoughts.
- Signs of an allergic reaction, like hives, swelling of the face or throat, or trouble breathing.
Who Should Not Take Phentermine?
Phentermine is not a good choice for everyone. Certain medical conditions can increase the possibility of having serious side effects.
You should not use phentermine if you:
- Have heart disease or high blood pressure that is uncontrolled
- An overactive thyroid (hyperthyroidism)
- Glaucoma
- You have taken MAO inhibitors within the last 14 days
- Are pregnant or breastfeeding
- Have a history of drug misuse
Medication Interactions: What Not to Mix
Phentermine can interact with other medications, which may increase side effects or create safety risks.
Important points to consider:
- Tell your doctor about all medications and supplements you are taking.
- Be cautious with other stimulants, including over-the-counter products.
- Never combine phentermine with MAO inhibitors.
- Some antidepressants may interact, depending on the type.
Your doctor and the pharmacist can help make sure your medication plan is safe.
Ways to Manage Phentermine Side Effects
You should never change your dose without medical advice, but there are steps that may help reduce your discomfort while taking phentermine.
Tips for managing common side effects:
- Dry mouth: Drink more water and try sugar-free gum or throat lozenges to help keep your mouth moist.
- Insomnia: Talk to your doctor about adjusting the timing of your dose to earlier in the day and limiting caffeine later in the day.
- Constipation: Drink plenty of water, gradually add fiber to your diet, and stay physically active. Check with your doctor before using laxatives.
- Jitters or anxiety: Avoid extra caffeine or stimulants, get plenty of rest, and manage your stress with calming activities.
Where Can I Learn More About Phentermine For Weight Loss?
You can obtain a prescription or learn more about phentermine for weight loss from Dr. Okeefe Simmons at Simmons MD Weight & Healthcare Solutions in Miami, FL.
Dr. Simmons is a board-certified gastroenterologist specializing in weight management. He has extensive experience in obesity medicine and has published research on obesity and digestive health.
He and his team of experts can review your medical history, current health, and lifestyle and help determine if phentermine would be a good fit for your situation. Dr. Simmons offers both in-office and telemedicine visits. Schedule your consultation today.
FAQS
How Long Do Phentermine Side Effects Last?
Most phentermine side effects are strongest in the first few days but usually get better after a few weeks. Many people find that symptoms improve as their body adjusts to the medication, but it can affect each person differently.
Can Phentermine Raise Blood Pressure or Heart Rate?
Yes. Phentermine may increase both heart rate and blood pressure, so usage should be closely monitored.
Is Phentermine Meant for Long-Term Use?
Phentermine is usually approved for short-term use. Long-term use may be considered depending on your individual situation and only under a doctor’s close supervision.
Can I Take Phentermine with Antidepressants?
Phentermine may interact with some antidepressants. Certain types can be taken safely under your doctor’s supervision, but others may cause serious side effects.
Important warning: Phentermine should never be combined with MAO inhibitors (MAOIs). These include medications such as Nardil (phenelzine), Parnate (tranylcypromine), Marplan (isocarboxazid), Emsam (selegiline), and Azilect (rasagiline). Combining phentermine with these drugs can lead to dangerous increases in blood pressure or other serious reactions.
Always talk with your prescriber before starting phentermine if you take any antidepressant or MAOI.
