Headaches are one of the most common side effects of phentermine. In fact, almost half of respondents in our online poll experienced this uncomfortable reaction.
The pain may be caused by either the pills or related lifestyle changes, but regardless, even a mild phentermine headache cansignificantly impact quality of life.
While not every person taking phentermine experiences headaches, it is still one of the most common reactions to this medication. New users and those that consume other substances alongside phentermine are more likely to experience head pain, as well as other negative side effects.
Headaches, and side effects in general, are more common at the beginning of treatment with phentermine.
The body takes some time to adjust to medication’s effects and, as with all chemical substances, some people react more strongly than others. So, for more sensitive patients, a phentermine headache may occur as the body adjusts to the new medication.
Lifestyle choices can also increase risk of headaches on phentermine. Due to the chemical interactions between substances, phentermine users who smoke, consume caffeine or drink alcohol are more likely to experience headaches.
Alcohol and phentermine interact negatively and can cause chest pain, increased blood pressure, dizziness, depression and sleepiness . Caffeine and nicotine are stimulants, so consuming them in combination with phentermine (an already-powerful stimulant) can also promote adverse reactions.
Phentermine headaches occur for a variety of reasons and it is hard to identify the precise cause exactly of each pain. However, some common explanations for a phentermine headache include:
Phentermine weight loss pills can cause headaches as a result of the active ingredient's stimulant effects. Phentermine is a sympathomimetic amine anorectic that stimulates the central nervous system to elicit a heightened state the similar to the “fight or flight” response .
One of the main effects of this activation response is tightening and narrowing of blood vessels (vasoconstriction) in the digestive organs and widening of blood vessels (vasodilation) in the skeletal muscles, heart, lungs and brain . The chemical changes associated with this response also increase heart rate and blood pressure to provide the muscles with the oxygen and nutrients they need .
These biological reactions also help explain the commonality of users reporting a phentermine headache. When cerebral arteries dilate (as part of the synthesized “fight or flight” response), blood flow increases to the brain. While brain tissue itself does not feel pain, the expansion of the blood vessels triggers surrounding nerves to send pain signals to your head and face . These signals may be responsible for your phentermine headache.
Another potential cause for a phentermine headache is dehydration.
This medication increases water needs and staying hydrated is critical to weight loss . Without enough water, tissues and blood vessels contract and electrolytes levels grow increasingly imbalanced. Both of these changes trigger head pain.
So, the trick to treating and preventing this type of phentermine headache is adequate fluid consumption each day.
Another common reason forphentermine headache is skipping meals or not eating enough. Following an overly-restrictive diet can cause headaches because, like a stimulant, dramatic changes in blood sugar or diet can alter hormones, which subsequently act on cerebral blood vessels and produce pain.
Long periods of fasting can also impact hormone levels and precipitate a phentermine headache. Due to hormonal changes in the body and brain, going many hours without eating may also trigger (or exacerbate) a hypoglycemic headache in some people.
Finally, skimping on shut-eye can cause headaches, or even migraines. Insomnia is a common phentermine side effect, so sleep problems are a widespread trigger of phentermine headaches.
Too much sleep, too little sleep or poor-quality sleep can call trigger or exacerbate headaches . Sleep problems contribute to head pain because the brain uses sleep to recharge and refuel. If you are depriving this vital organ of its much-needed rest, headaches can ensue.
Like most side effects, phentermine headaches tend to decrease or disappear after a couple of weeks, or after the patient adjusts to the medication. However, if you are early in treatment and battling a bothersome phentermine headache, you are probably wondering how to prevent a headache while taking Adipex or other brands of phentermine.
The first step is to avoid phentermine headache triggers when possible. Some common triggers include that 3pm coffee, a tendency to skip breakfast or a constant state of sub-optimal hydration. So, if your head is constantly throbbing, consider these simple changes to get rid of a mild phentermine headache:
Aim for at least two liters of water or other caffeine-free, calorie-free beverages per day, and more if your pee is not light yellow [9,10]. When you feel a phentermine headache coming on, drink 2-3 glasses of water right away. If the headache is caused (or worsened) by dehydration, this should start bringing relief in about 30 minutes to 3 hours. Caffeinated and alcoholic beverages worsen dehydration, so favor caffeine-free, sugar-free drinks to promote proper hydration.
To minimize blood sugar-related headaches, try to eat every 4-6 hours while awake. If you have diabetes or other troubles regulating your blood sugar, it may be beneficial to aim for a meal or snack every 3-4 hours. Aim for a combination of complex carbs (whole grains, fruit, vegetables) and lean protein at each meal or snack to keep blood sugar level. If there is no time for a proper meal, grab a meal replacement shake or pre-packed snack.
Eating too little, even if consumed frequently throughout the day, can also cause a hypoglycemic phentermine headache. Small snacks should be around 100-250 calories each, and women should consume at least 1200 calories a day, while men need 1500 calories a day to support basic biological functions.
To prevent a sleep-related phentermine headache, aim for 7-9 hours of high-quality sleep per night . If the medication is keeping you up, try taking your pill first thing in the morning so that you give the phentermine as much time as possible to wear-off before you head to bed.
If your headache is relatively mild and short-lived, you may be able to treat it with over-the-counter (OTC) pain killers. Common pain relievers you can take for a headache while on phentermine include Tylenol (acetaminophen), Motrin (ibuprofen) or Aleve (naproxen) . However,it is important not exceed the recommended dose or combine these medications, and always make sure to take the pills with plenty of water.
See a doctor if your phentermine headache is not completely controlled with reasonable at-home treatment.Talk to him or her if your headache lasts more than a couple of days or interferes with your normal daily activities.
If you are taking a high dose of phentermine and the headaches (or other side effects) are not going away, it may be worthwhile to speak with your doctor about decreasing the dose. NEVER adjust your dosage or schedule without first speaking to your prescribing doctor.
Learn more about phentermine!
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2. National Center for Biotechnology Information. PubChem Compound Database: CID=4771 (Phentermine).
3. Linder, T., Ph.D., & Melby, A. E., Ph.D. (2017, April 14). Control of Arterioles.
4. BBC Science & Nature. (2014, September 24). Human Body and Mind - Nervous System Layer.
5. Marcus, D. A. (2004, May 24). What causes headaches?
7. The Migraine Trust. (n.d.). Hypoglycaemia.
8. Rains, J., Ph.D. (n.d.). Sleep Disorders and Headache.
9. NHS Inform. (2019). Hydration.
10. Mayo Clinic Staff. (2017, September 06). Water: How much should you drink every day?
11. National Sleep Foundation. (2014, November 13). How to Fall Asleep Fast.