If you get thirsty or your mouth feels dry right after smoking cannabis, you might come to the logical conclusion that cannabis causes dehydration. Considering that dry mouth is one of cannabis’ signature side effects, the question of whether this dry mouth is caused by dehydration comes up often. 

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If you’re dehydrated when smoking cannabis, chances are you were already dehydrated from drinking too little water or you could have an underlying illness that’s causing your condition, because Cannabis doesn’t generally cause dehydration. 

Dehydration, the Mayo Clinic explains, is a health problem that occurs when your body loses or uses more fluid than it’s taking in and this results in your body not having enough water or fluid to do its ordinary business, such as flush out toxins via urine or cool you down through sweat. Anyone can become dehydrated and the condition is usually easily fixed through drinking water. 

Thirst isn’t a good early indicator of dehydration, the clinic explains, as many people don’t feel thirsty until they’re already dehydrated. This also gives us some insight into why dehydration likely isn’t the cause of that dry mouth if you’re experiencing it right after consuming cannabis and you felt fine earlier. 

Other symptoms of dehydration include dark urine, fatigue, dizziness, and confusion, so if you’re a regular marijuana user, the typical side effects of using the herb, which can also include dizziness and feeling dazed, could easily be confused with dehydration.

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Woman wearing denim shirt working in the office and opening plastic bottle of water iStock / Kerkez

A Rare Cause Of Dehydration Connected To Cannabis 

There’s one case where your dehydration may actually be caused by cannabis, as in the case of cannabinoid hyperemesis syndrome (CHS).

According to a recent report in the British Medical Journal, this rather rare event occurs in about 6% of patients who present to emergency departments with recurrent vomiting in one retrospective study. 

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Manifesting in daily, long-term users, so dabblers aren’t likely to be affected, and includes symptoms of severe vomiting, which can lead to a significant fluid loss over time.

First described in 2004, CHS associates cyclic nausea and vomiting with abdominal pain in regular cannabis users.  Patients report that they have to resort to hot showering - compulsively - or bathing in warm water to alleviate symptoms (encountered in 90-100% of reported cases). In fact, this feature is so common that such activity along with the vomiting been proposed as a diagnostic criteria.

It turns out that the digestive tract has a number of molecules that bind to THC, according to Cedars Sinai. That means marijuana can affect the digestive tract in a number of ways, such as changing the time it takes the stomach to empty. 

In the brain, marijuana helps prevent nausea and vomiting, but it has the opposite effect in the digestive tract. “With the first use of marijuana, the signals from the brain may be more important. That may lead to anti-nausea effects at first. But with repeated use of marijuana, certain receptors in the brain may stop responding to the drug in the same way. That may cause the repeated bouts of vomiting found in people with CHS,” the hospital explained. It’s also not clear why some heavy users develop the condition and others don’t. 

The condition can be divided into three stages, with the first stage involving early morning nausea and belly pain and the second involving ongoing nausea and vomiting, eating less food, weight loss, and dehydration. The final phase is the recovery phase, which begins when the person completely stops using marijuana.

According to research published in the Journal of Emergency Medicine, the condition has become more prevalent as legalization spreads throughout the country and as cannabis potency increases. Topical capsaicin cream, which alleviates muscle pain, holds promise as a treatment but the only assured cure is to stop using cannabis.

Dry Mouth and Cannabis


woman inhales from pot joint

If dehydration isn’t the likely culprit for feelings of thirst associated with cannabis, what is? Dry mouth is one of the most common side effects of using the drug, according to results from a 2019 survey published in The Journal of Alternative and Complementary Medicine. “The most commonly endorsed acute effects were improved sleep, more calm/peaceful, desire to eat, more creative, and dry mouth; while the most commonly endorsed withdrawal symptoms were irritability, insomnia, and anxiety,” the survey stated. 

Around 63 percent of survey respondents reported symptoms of dry mouth, compared to 82 percent reporting improved sleep in the physiological effects category.

The survey participants were reporting what we commonly call cottonmouth and it’s caused by a decrease in saliva secretion. The THC in cannabis attaches to two types of cannabinoid receptors, CB1, and CB2, which are located in the submandibular (SMG) salivary gland. Both CB1 and 2 play a role in mediating the effects of THC; in this case, the THC sends a message to slow saliva production, which results in dry mouth.

In most cases, the symptom of dry mouth is not dangerous, though over time a decrease in the amount of saliva in your mouth could cause problems by allowing more bacteria to flourish, contributing to plaque, and potentially leading to gum inflammation and tooth decay.

How To Deal With Dehydration And Dry Mouth

If you’re using cannabis and you experience dry mouth, use a sugar-free drink to rinse out your mouth instead of sodas or sports drinks, which may look healthy but often have high sugar contents. You can also chew on ice, use a lozenge or cut back on how much you’re smoking to reduce the amount of THC in your system.

If you’re dehydrated before going into a smoke session, you may confuse marijuana as the culprit. Drinking plenty of fluids should cure thirst associated with dehydration, but if it doesn’t, you may want to see a medical professional about potential underlying conditions, such as diabetes, kidney disease or adrenal gland disorders, that may be contributing to the problem. 

It’s not normal to feel dehydrated over the long-term, so be sure to get checked out if dry mouth and thirst persist long after you finish smoking.