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Phentermine Vs. Adderall: How Do These Two Stimulants Differ?

Adderall versus phentermine
Written by:

Wafaa Amjad Dar


Dr. Bradley Noon



Medical Disclaimer
The medications listed on this website are provided for informational purposes only. Their inclusion does not guarantee that they will be prescribed to any individual, as treatment decisions are ultimately at the discretion of healthcare providers. This list is not exhaustive, and healthcare providers may prescribe other medications, including non-stimulant options, based on the patient’s unique health circumstances and needs.Read more
The medications listed on this website are provided for informational purposes only. Their inclusion does not guarantee that they will be prescribed to any individual, as treatment decisions are ultimately at the discretion of healthcare providers. This list is not exhaustive, and healthcare providers may prescribe other medications, including non-stimulant options, based on the patient’s unique health circumstances and needs.

Both phentermine and Adderall are stimulant medications, but they have several differences. Phentermine is the active component in Adipex-P [1*] , which is FDA-approved to treat obesity. Adderall [2*] contains amphetamine and dextroamphetamine salts and is used for the management of attention deficit hyperactivity disorder (ADHD) and narcolepsy. Below, let’s explore the differences between phentermine and Adderall in more detail.

See a qualified medical provider to get the most appropriate treatment for your mental health condition.

Phentermine vs Adderall: Mode of Action

Phentermine and Adderall are similar in their mechanism of action. Both are CNS stimulants: they stimulate the brain, accelerating mental and physical processes. Aside from other effects, they primarily raise the concentrations of one or more neurotransmitters in the brain, such as dopamine, norepinephrine, and serotonin.

How They Work for Relevant Conditions

As further classified CNS stimulants, Phentermine and Adderall are sympathomimetic amines. Adderall increases the levels of norepinephrine and dopamine. It also enhances the activity of brain regions controlling focus, attention, and impulse control, leading to improved ADHD symptoms. It has some effect on the brain regions controlling hunger, so it may contribute to weight loss off-label [3*] .

Phentermine [4*] works like Adderall in terms of stimulating the release of norepinephrine and dopamine. But it acts as an anorectic and promotes appetite suppression, increased satiety, and a boost in energy expenditure. These effects lead to weight loss when combined with physical activity.

Is Phentermine Used for ADHD?

Because of its similarity to amphetamines, phentermine may be used off-label to treat ADHD. It is viable that escalating norepinephrine concentration levels in the brain could help improve attention and reduce impulsivity. However, it is not FDA-approved for this condition, and there is no extensive research on its effectiveness in this case.

Phentermine vs Adderall

Phentermine and Adderall comparison before prescribing them usually includes an overview of the patient’s diagnosis and the medications’ specifics. For example, common side effects, dosage, and precautions. Let’s delve into these aspects below.


For hunger control, the average adult dose of phentermine [5*] is one capsule (37.5 mg) per day, 1 to 2 hours before breakfast, if not prescribed otherwise. Adderall, on the other hand, has a starting dose of 5 mg once or twice daily; with 5 mg increments at weekly intervals until reaching optimal response. The dose may vary depending on the symptoms and individual health features, so your doctor may adjust it accordingly.

See our experts online to get your ADHD symptoms assessed and obtain a personalized treatment plan.


Common side effects of Adderall [6*] include:

  • Rapid or irregular heartbeats
  • Insomnia
  • Hypertension
  • Tremors
  • Lightheadedness
  • Muscle twitching
  • Hallucinations
  • Dizziness
  • Diarrhea or constipation
  • Alterations in mental state
  • Headaches
  • Sexual impotence

Common side effects of phentermine include:

  • Unpleasant taste
  • Palpitations
  • Diarrhea
  • Insomnia
  • Headache
  • Nervousness
  • Dry mouth or vomiting
  • Changes in libido
  • Constipation

If used for an extended period of time, both medications have the potential to cause physical dependence. Keep in touch with your healthcare provider and follow their instructions to prevent such effects.


Despite being helpful in managing weight loss and ADHD, these medications have several precautions. A few associated with Adderall are the following:

  • Patients with pre-existing heart problems or high blood pressure have to regularly monitor their heart rate.
  • It’s important to watch out for mood changes, agitation, or hallucinations to avoid exacerbation of mental health conditions.
  • Patients who are pregnant, planning to conceive, or breastfeeding must discuss potential risks with their healthcare provider.
  • One should not increase dosage without medical supervision because the medication has the potential for dependence or abuse.
  • One should avoid driving or operating machinery until the effects of the medication on alertness become clear.
  • It’s not recommended to consume alcohol and other stimulants, as this can increase the risk of adverse effects.

Some precautions to consider with phentermine use include:

  • Short-term use only. It should be used as prescribed and without extending its use beyond the doctor’s recommendation.
  • People with impaired liver or kidney function should use it with caution.
  • Patients with health conditions have to monitor heart rate and blood pressure because the medication can increase them.
  • Avoid driving or operating heavy machinery until you know how the medication affects you. 
  • The body may develop tolerance, decreasing the medication’s effectiveness over time.
  • Abrupt discontinuation can lead to withdrawal symptoms.
  • Some patients may need to lower doses of their insulin or oral diabetes medication.
  • Patients who are pregnant or breastfeeding should avoid taking phentermine.

Over-the-counter Alternatives

Phentermine and Adderall are prescription medications, but there are a few over-the-counter (OTC) solutions for weight loss and ADHD management. However, it’s critical to consult with a healthcare professional before using OTC alternatives, as they may pose health risks or interact with other medications.

OTC solutions for weight loss [7*] may include the following:

OTC supplements for improving ADHD symptoms [9*] may include:

  • L-Theanine
  • Omega 3 fatty acids
  • Zinc and Magnesium supplements
  • Iron
  • Ginseng
  • Vitamin B6

However, the effectiveness and safety of these OTC supplements vary, and they may not be suitable for everyone.

Always consult a medical expert before taking any medication. Get in touch with our team to get the most appropriate evidence-based treatment.

Drug Interactions



  • Monoamine oxidase inhibitors (MAOIs)
  • SSRIs
  • Tricyclic antidepressants 
  • Other stimulants and weight loss medications 
  • Antihypertensives
  • Monoamine oxidase inhibitors (MAOIs)
  • Cardiovascular drugs
  • Tricyclic antidepressants
  • Other stimulant medications
  • Antihypertensives
  • Antacids
  • Proton pump inhibitors
  • Thiazides
  • Antihistamines
  • Phenobarbital
  • Phenytoin

Can You Take Adderall And Phentermine Together?

Phentermine and Adderall have a major interaction as both of them are stimulant medications. Since they share a similar chemical structure to amphetamine salts, they have identical physiological effects on the body. Taking two sympathomimetic drugs simultaneously can significantly increase the risk of serious cardiovascular and nervous system side effects such as increased heart rate, high blood pressure, and irritability. Therefore, they should not be combined in most cases.

Can Phentermine Make You Feel High?

Phentermine works by sending signals to your brain that tell you whether you’re hungry or not. When combined with adrenaline, it causes your body to boost fatty acid and glucose levels while also breaking down stored fat, increasing energy production. This stimulates your body to increase activity levels, allowing the adrenaline rush of energy to find a home. But the effects are generally not euphoric or intoxicating. However, like any medication, individual responses can vary.


Adderall is commonly prescribed for ADHD, while phentermine is used for weight loss. However, their off-label uses may overlap. Note that both medications can cause side effects and dependence, so seek professional advice on the most suitable treatment and keep in touch with your healthcare professional during the whole process.


Yes, a healthy lifestyle can support the effectiveness of these medications. These include maintaining a balanced and nutritious diet, engaging in regular physical activity, ensuring adequate quality sleep, staying hydrated, and participating in stress-reducing activities.
Phentermine is favored as a weight loss medication for its affordability and proven effectiveness in weight loss, but individual factors like medical history and long-term goals are also considered. Adderall, one of many ADHD treatments, is chosen depending on factors such as symptom severity, comorbid conditions, and individual response to treatment.
Healthcare professionals consider factors such as medical history, weight loss goals, detailed ADHD symptom evaluation, and the side effect profiles of each medication.
Yes, it is a stimulant medication. It belongs to a class of sympathomimetic amines, which work by stimulating the central nervous system to suppress appetite. This stimulant effect helps individuals feel full more quickly and consume fewer calories, which aids in weight loss efforts.
These are distinct medications with different primary uses and mechanisms of action. Adderall is primarily prescribed for managing ADHD, while phentermine is approved for short-term weight loss. They cannot be directly substituted for each other without careful consideration by a healthcare professional.
Acclimating to this medication varies individually; effects typically appear within days to weeks after starting. However, full adaptation to it may take several weeks.
Yes, your body can adjust to it over time. At first, you may experience noticeable effects, but with time, your body may become accustomed to them, and you may not perceive them as strongly as when you first started. It’s essential to follow your healthcare provider’s guidance, monitor any changes in your response to medication, and never stop treatment abruptly without consulting your healthcare provider first.


9 sources
  1. Adipex-P
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  2. Adderall
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  3. Piloting a New Approach to the Treatment of Obesity Using Dexamphetamine
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  4. Effects on Weight Reduction and Safety of Short-Term Phentermine Administration in Korean Obese People
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  5. Phentermine
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  6. Potential Adverse Effects of Amphetamine Treatment on Brain and Behavior: A Review
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  7. https://pubmed.ncbi.nlm.nih.gov/15554492/
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  8. Orlistat, a New Lipase Inhibitor for the Management of Obesity
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  9. Complementary medicines (herbal and nutritional products) in the treatment of Attention Deficit Hyperactivity Disorder (ADHD): a systematic review of the evidence
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Written by:

Wafaa Amjad Dar


Dr. Bradley Noon



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Evidence Based

This article is based on scientific evidence, written by experts and fact checked by experts.

Our team of experts strive to be objective, unbiased, honest and to present both sides of the argument.

This article contains scientific references. The numbers
in the parentheses (1, 2, 3) are clickable links to peer-reviewed scientific papers.