Does Phentermine Cause Heartburn and Acid Reflux?

January 9, 2024 |

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In this article, I will discuss if phentermine causes heartburn and how you can cope with it.

Many users have complained of developing acid reflux with phentermine, but the scientific communities are yet to identify the exact mechanism that causes it.

Nonetheless, the role of phentermine in keeping you away from food for too long seems like the most reasonable justification for this (acid reflux) heartburn. Other factors like your gender, age, and taking the drug long-term may also make you more prone to developing this side effect.

To explain in detail what could possibly be the reason behind your heartburn symptoms, I’ve shared some medical evidence, along with tips for treating it.

So, keep reading to find out all this and more about it.

Why Does Phentermine Cause Heartburn?

If you are suffering from heartburn after taking phentermine, then you may be predisposed to it, or there may be some secondary reasons that are causing it.

Considering it is a rare side effect, scientists have yet to perform significant research to find and confirm the correlation between the two.

But still, here are some justifications that might explain why you are having such symptoms.

An Empty Stomach

Phentermine aids your weight loss by helping you ‘starve’ for longer with its appetite-suppressing effect.

On that account, not eating for extended periods may lead to acid accumulation in the stomach. And as a consequence, the excess acid may regurgitate into your throat, causing a burning feeling in your chest, which you may describe as heartburn or acid reflux.

Susceptibility In Certain Populations

A phase IV clinical study of FDA data created by eHealthMe reveals that only 0.56% of people have reported having GERD with phentermine.

Out of these, a majority of 82.89% were females, while just 17.11% were males.

Also, it was more common among 40–49-year-olds and those who have been taking the drug for 5 to 10 years.

These numbers show that the age, gender, and duration of phentermine use may increase the risk of this side effect in some people as compared to others, but the exact reason is unknown.

Here’s What My Ingredient Investigation Revealed

Although the above two sections somewhat explain why phentermine may flare up GERD, when I reviewed its formulation, I could not find many ingredients that might be the culprits.

For instance, its inactive ingredients like dibasic calcium phosphate dihydrate and magnesium stearate basically neutralize the pH of the stomach acid.

Other additives like shellac glaze and crospovidone are commonly added to antacid tablets as well, which means that they may not aggravate stomach acidity.

The only ingredient that can be blamed for causing the uncomfortable symptoms is propylene glycol which becomes acidic as it begins to degrade in the stomach.

Additionally, experts on and have also weighed in with the opinion that phentermine does not cause acid reflux or aggravate GERD.

So, it would best help if you discuss your symptoms with a doctor to have personalized advice.

Can I Take Antacids With Phentermine? (For Treating Heartburn?)

No, you should not take antacids with phentermine as it is contraindicated with them.

As I mentioned above, phentermine pills contain magnesium and calcium salts which may already have a role in neutralizing the stomach acid pH. Therefore, taking antacids on top of phentermine may further alkalize the stomach, which can affect the pH-dependent excretion process of phentermine.

A study on the effect of antacid intake on urine pH also reveals that consuming antacids may increase the pH of urine, making it basic and thus causing phentermine to stay in the system for longer.

This may have two consequences; it may either prolong the duration of the appetite-suppressing effect of phentermine or amplify its risks to the body’s systems.

For reference, according to the data regarding phentermine available on PubChem, the mean terminal half-life of phentermine varies between 19-20 hours in normal conditions. However, when the pH of urine is acidic (pH <5), the elimination half-life is reduced to 7-8 hours.

How To Treat Heartburn Caused By Phentermine?

acid reflux

Since you can’t take antacids with phentermine, here are some things you can do to stop your stomach acid from jumping up to your mouth.

Drink Enough Water

Pay attention to your water intake and drink at least 8 glasses of water throughout the day with phentermine.

It will not only help you get rid of water weight but will also dilute the stomach acid and flush it out.

Chew On A Gum

According to one research, chewing on sugar-free gum can prompt the act of swallowing.

A higher swallowing frequency was found to promote the clearance of the esophagus from stomach acid, thus, helping to reduce the symptoms of heartburn.

Eat A Ripe Banana

Bananas perfectly complement phentermine because they reduce the risk of its side effects while simultaneously boosting its weight loss benefit.

Regarding acid reflux, according to US FDA, the pH of a ripe banana is neither too acidic nor basic, making it ideal for neutralizing stomach acidity without hindering phentermine elimination.

Furthermore, an average banana offers approximately one hundred calories of energy which may help to support your workout routine.

On the nutritional side, bananas are low glycemic and are rich in fiber, vitamins, and minerals; hence, they may help nourish your body and prevent micronutrient deficiencies due to calorie-restricted diets.

According to, bananas have a satiety index greater than white bread (118% vs. 100%), and thus, they may enhance appetite suppression. And this is not all; they may also prevent high blood pressure, which is another side effect of phentermine.

Consult Your Doctor

If all else has failed, and your acid reflux doesn’t get any better with all these remedies, I would recommend you immediately pause your phentermine medication and consult with the doctor that recommended it to you in the first place.

Bottom Line

To conclude, users do complain of heartburn with phentermine, but the incidence rate is very low.

Besides, for now, there is a lack of solid scientific evidence to support this link.

Nonetheless, phentermine kills food cravings, leaving you empty stomach for long periods of time and thus spiking the acidity in there. You can try countering that acid buildup by eating light meals throughout the day and increasing your water intake.

Or you may try eating bananas as a natural acid reflux remedy while simultaneously benefiting from their nutritional properties.

Last but not least, consult a doctor if symptoms don’t resolve, and DON’T take antacids with phentermine.

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