Why do antibiotics make you thirsty?

In this article:

• Do antibiotics make you thirsty?
• Antibiotics and dehydration
• Water intake on antibiotics
• When to see a doctor

In this article

• Do antibiotics make you thirsty?
• Antibiotics and dehydration
• Water intake on antibiotics
• When to see a doctor

Often heralded as one of humankind’s greatest accidental discoveries, antibiotics fight bacterial infections by either killing bacteria or stopping their growth. This makes them essential tools in treating conditions like bacterial pneumonia, urinary tract infections, and strep throat. 

As one of the most frequently prescribed medications, the link between antibiotics and thirst isn’t as often discussed as some more common side effects. While antibiotics don’t directly cause thirst or dehydration, they can certainly lead to dry mouth and feeling parched through a few different mechanisms.

Do antibiotics make you thirsty?

It’s not in your head—and it’s not the pretzels, either: Some antibiotics can make you thirsty, but in a roundabout way. Certain antibiotics slow down saliva production, which causes dry mouth, leading to increased thirst and, likely, increased water intake. 

While it may seem odd, the connection between dry mouth and increased water consumption is relatively straightforward: Some antibiotics interfere with how the salivary glands work. They block or weaken the signals that tell the glands to release saliva and reduce how well the cells can move water into the saliva. In short, saliva flow is reduced, and dry mouth sets in.

“Antibiotics disrupt the normal oral microbiome, shifting the local environment of the salivary glands and reducing mechanical/chemical signals for saliva production,” says James Lyons, MD, provider at Synergy Houses in Austin, Texas.

Since saliva is 99% water, reduced production creates oral dryness and discomfort that causes thirst. According to Steven Goldberg, MD, Chief Medical Officer at HealthTrackRx, several specific antibiotics have been clinically documented to cause dry mouth:

• Penicillins, including amoxicillin
• Clindamycin
• Metronidazole
• Macrolides, including erythromycin, clarithromycin, and azithromycin
• Tetracyclines, including doxycycline and tetracycline
• Linezolid
• Fluoroquinolones, including ciprofloxacin

That being said, while dry mouth can happen with some medications, it’s not a common side effect of most antibiotics.

Can antibiotics cause dehydration?

While antibiotics themselves don’t cause dehydration, other antibiotic-related side effects, such as diarrhea and vomiting, can lead to fluid loss. Because gastrointestinal side effects are relatively common when taking antibiotics, it’s likely that this is how people came to associate antibiotics with dehydration.

Jeffrey Chester, DO, Medical Director at The Ohana Treatment Center in Kailua, Hawaii, confirms this relationship: “Antibiotics can cause some patients to experience dehydration because they cause gastrointestinal side effects like diarrhea, which can increase the risk of dehydration significantly.”

While it may seem like an obvious link, dry mouth itself doesn’t necessarily indicate more systemic dehydration in the body. Instead, the increased thirst that some people experience while taking antibiotics is more likely a localized response to reduced saliva production. However, if you’re experiencing a dehydrating gastrointestinal event, it’s important to ensure you’re replenishing any lost fluids.

Should you drink more water with antibiotics?

Getting your eight glasses per day while taking antibiotics is important for a variety of reasons, including supporting kidney health, potentially reducing side effects, and staying hydrated while your body fights the infection that led to antibiotic use.

“Proper hydration supports kidney perfusion, dilutes toxins, and reduces the risk of kidney injury,” says Dr. Goldberg. This is especially important because antibiotic-induced kidney dysfunction is a leading cause of acute kidney injury in hospitalized patients.

For a healthy adult on antibiotics, healthcare professionals typically recommend 2-3 liters (8-12 cups) per day of total fluids. Yes, that means teas, broths, and juices all count toward your total liquid intake. One caveat: When taking antibiotics and tallying your water intake, it’s best to avoid beverages that can worsen dry mouth and dehydration, including alcohol and caffeine. 

If you experience antibiotic-associated diarrhea or vomiting, Dr. Goldberg recommends oral rehydration solutions, including electrolyte-supported beverages, as first-line therapy. While electrolyte monitoring isn’t usually necessary for short-term antibiotic use, he notes it’s recommended during long-term therapy, especially for nephrotoxic antibiotics (antibiotics that can harm the kidneys).

Those with kidney disease or heart conditions should speak with their healthcare provider to determine specific fluid intake guidelines that best suit their conditions. 

When to see a healthcare provider

While most antibiotic-related dry mouth is safe to treat and monitor yourself, complications can arise that require hands-on intervention. If your dehydration is mild, you have manageable thirst, aren’t experiencing any ulcers as a part of your dry mouth, and you’re able to rehydrate orally after experiencing any gastrointestinal side effects, self-management is an acceptable path.

However, more severe dehydration or other more serious side effects warrant medical attention. According to Dr. Goldberg, you should seek medical advice immediately if you experience:

• Severe dehydration that doesn’t respond to oral hydration
• Persistent vomiting or diarrhea, limiting fluid intake
• Low amount of urine output or dark urine
• Confusion or altered mental status
• Severe dry mouth
• Discoloration of the skin or eyes
• Chest pain or rapid heart rate
• Severe dizziness or fainting
• Shortness of breath or trouble breathing

If dehydration is a concern for you, Dr. Goldberg recommends tracking your symptoms and water intake, recording instances of abdominal pain, vomiting, diarrhea, dry mouth, and urine changes. This makes it easier to spot any abnormalities and effectively communicate them to your provider if needed.

While mild dry mouth and increased thirst are manageable side effects of certain antibiotics, staying properly hydrated and monitoring for more serious symptoms is important while taking this type of medication. Further, it’s crucial that you seek immediate medical attention if you suspect you are having an allergic reaction, like a skin rash, hives, swelling, or trouble breathing.

The bottom line

While antibiotics can make you feel thirsty, primarily through their ability to cause dry mouth, they don’t themselves cause dehydration. Certain antibiotics like clindamycin, metronidazole, and various macrolides and tetracyclines are known to reduce saliva production, which causes the sensation of dry mouth and can lead to drinking an increased amount of water.

The more significant concern for dehydration comes from antibiotic-induced gastrointestinal side effects like diarrhea and vomiting, which can lead to fluid and electrolyte losses. Maintaining adequate hydration while taking antibiotics is essential not only for managing these side effects but also for supporting kidney function and ensuring proper medication elimination.

Most patients can safely manage mild dry mouth and associated thirst with increased water intake and good oral hygiene. However, it is important to actively monitor for signs of a more serious issue, like persistent vomiting, severe diarrhea, or decreased urination. When in doubt, don’t hesitate to contact your healthcare provider. They can help distinguish between normal, manageable side effects and symptoms that require immediate attention.