What STD Causes Diarrhea? Common STDs That May Trigger GI Symptoms

Experiencing diarrhea or stomach pain after sex can be confusing and understandably concerning. Most diarrhea is caused by everyday issues like food poisoning, viral stomach bugs, or stress. However, in certain situations, gastrointestinal (GI) symptoms can be linked to a sexually transmitted disease (STD), especially after oral or anal sexual exposure.

So, what STD causes diarrhea? While it’s not the most common symptom, several STDs can affect the rectum or intestines and lead to diarrhea, abdominal discomfort, or rectal symptoms. Understanding when diarrhea might be STD-related and when to get tested, can help you take the right next step for your health. At Manhattan STD Testing, we help patients across Manhattan and Forest Hills get clear answers quickly with confidential, same-day STD testing options.

Can an STD Cause Diarrhea or Stomach Pain?

Yes, an STD can make your stomach hurt or cause diarrhea, but this typically happens under specific circumstances. STDs that infect the rectum or spread systemically through the body can trigger inflammation in the gastrointestinal tract.

GI symptoms are often overlooked in STD diagnosis because they overlap with many non-sexual illnesses. Medical organizations such as the Mayo Clinic and Cleveland Clinic note that infections affecting the rectum or immune system can sometimes present with gastrointestinal symptoms, making sexual history an important part of evaluation. According to the CDC and infectious disease guidelines, rectal STDs are more likely when exposure involves:

• Anal sex (insertive or receptive)
• Oral–anal contact (rimming)
• Unprotected sexual contact

In these cases, diarrhea may be accompanied by rectal pain, mucus, bleeding, or persistent abdominal discomfort.

Is Diarrhea a Symptom of an STD?

Usually no, but sometimes yes. Diarrhea is not a classic STD symptom for most infections. However, it can occur when an infection involves the rectum or intestines, or during early systemic infections like acute HIV.

STD-related diarrhea is more likely when:

• There has been recent oral–anal or anal sexual exposure
• Diarrhea is persistent, recurrent, or unexplained
• Symptoms include rectal pain, mucus, bleeding, or urgency
• GI symptoms occur alongside fever, fatigue, rash, or swollen lymph nodes

Because diarrhea has many non-sexual causes, testing helps distinguish an STD from common illnesses like food poisoning or viral gastroenteritis.

Common STDs That Can Cause Diarrhea

Chlamydia (Rectal Chlamydia)

Rectal chlamydia is one of the more common answers to what STD causes diarrhea.

Possible symptoms include:

• Diarrhea or loose stools
• Rectal pain or pressure
• Mucus or blood in stool
• A constant urge to have a bowel movement

Many people have no symptoms at all, which is why chlamydia testing is important. Rectal chlamydia is diagnosed with a rectal swab and is easily treated with antibiotics when caught early.

Gonorrhea (Rectal or Pharyngeal)

Gonorrhea can infect the rectum and, less commonly, contribute to GI symptoms.

Symptoms may include:

• Diarrhea
• Abdominal discomfort
• Rectal discharge or itching
• Pain during bowel movements

If you’re wondering what STD makes your stomach hurt, rectal gonorrhea is a possible cause—especially after unprotected anal sex.

Syphilis

Syphilis doesn’t usually start with diarrhea, but GI symptoms can occur during secondary syphilis, when the infection affects multiple organ systems.

Possible signs include:

• Diarrhea or abdominal pain
• Fever
• Rash (often on palms or soles)
• Fatigue or swollen lymph nodes

Because syphilis progresses in stages, early testing is critical.

HIV (Acute Infection Phase)

During early or acute HIV infection, diarrhea and stomach pain are common symptoms. The World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) both recognize gastrointestinal symptoms as part of early HIV seroconversion illness.

These are often accompanied by:

• Fever
• Fatigue
• Sore throat
• Muscle aches

If you’re experiencing diarrhea after sex along with flu-like symptoms, HIV testing is strongly recommended. Early diagnosis allows for prompt treatment and better long-term outcomes.

LGV (Lymphogranuloma Venereum)

LGV is a more aggressive strain of chlamydia that primarily affects the rectum.

It can cause:

• Severe diarrhea
• Rectal bleeding
• Abdominal pain
• Symptoms that mimic inflammatory bowel disease

LGV requires specific antibiotic treatment and should not be ignored.

Sexually Transmitted Enteric Infections (STIs That Affect the Gut)

Not all sexually transmitted infections that cause diarrhea are considered classic STDs. Some enteric infections affect the intestines and are spread through fecal–oral exposure, which can occur during certain sexual activities.

Sexually transmitted enteric infections may include:

• Shigella: often causes sudden diarrhea, abdominal cramps, and fever
• Campylobacter: can lead to diarrhea (sometimes bloody), stomach pain, and nausea
• Giardia: may cause persistent diarrhea, bloating, and gas
• Salmonella: can cause diarrhea, fever, and abdominal cramps

These infections are more commonly reported after:

• Oral–anal contact
• Unprotected sex
• Sexual contact during or shortly after a diarrheal illness

While these are not always classified as traditional STDs, they are sexually transmissible infections and should be evaluated with medical testing, especially when diarrhea develops after sexual exposure.

What STD Causes Stomach Pain and Diarrhea Together?

STDs most likely to cause stomach pain and diarrhea together include:

• Rectal chlamydia
• Rectal gonorrhea
• LGV
• Acute HIV

In these infections, inflammation of the rectum or intestines disrupts normal digestion and bowel function, leading to cramping, urgency, and loose stools.

How Soon Can Diarrhea Start After Sexual Exposure?

One of the most common questions people ask is how quickly diarrhea can appear after sex. The timing can offer helpful clues about whether symptoms are more likely related to an STD or a common gastrointestinal illness.

STD-related diarrhea usually does not start immediately after sex. Symptoms that persist, worsen, or appear alongside rectal discomfort or flu-like signs are more likely to require STD testing.

Diarrhea After Sex: When Should You Be Concerned?

You should consider STD testing if you have diarrhea after sex and:

• Recently had unprotected oral or anal sex
• Symptoms last more than 2–3 days
• You notice rectal pain, bleeding, or mucus
• You also have fever, fatigue, or rash

These signs don’t confirm an STD, but they do warrant medical evaluation.

STD-Related Diarrhea vs Common GI Illness

If diarrhea keeps coming back or doesn’t improve, testing helps rule out infections.

How STD-Related GI Symptoms Are Diagnosed

At Manhattan STD Testing, diagnostic testing is discreet, judgment-free, and tailored to your symptoms and sexual exposure, ensuring you receive the right tests without unnecessary delays.

Diagnosis may include:

• Rectal swabs for chlamydia and gonorrhea
• Blood tests for HIV and syphilis
• Stool testing (when appropriate)

Being open about sexual practices helps providers choose the right tests and ensures accurate results.

Treatment Options

Treatment depends on the infection:

• Bacterial STDs: Antibiotics
• HIV: Antiretroviral therapy
• Supportive care: Hydration and symptom relief

Avoid sexual contact until treatment is completed and partners are notified.

Can STD-Related Diarrhea Go Away on Its Own?

Symptoms may temporarily improve, but untreated STDs often persist or worsen. Delaying treatment can lead to complications and continued transmission.

When to Get Tested in Manhattan, NYC

Consider testing if you have:

• Diarrhea with recent sexual exposure
• Ongoing GI symptoms with no clear cause
• A partner diagnosed with an STD

Early testing means faster treatment and peace of mind. Manhattan STD Testing offers fast, confidential STD testing in Manhattan, NYC, making it easy to get answers and start treatment if needed. If symptoms are unclear or multiple infections are possible, a comprehensive STD panel can screen for several STDs at once and help identify the cause quickly.

Prevention Tips

• Use condoms or dental dams during oral and anal sex
• Get routine STD screenings
• Communicate openly with partners

When To See A Doctor Immediately

If your symptoms feel intense, alarming, or simply “not right,” trust your instincts—getting medical care early can prevent complications and provide quick answers.

Seek urgent care for:

• Severe or worsening abdominal pain
• Bloody diarrhea
• Signs of dehydration
• Persistent fever

Conclusion

STD-related diarrhea is uncommon but very real and treatable once identified. If you’re experiencing GI symptoms after sexual exposure, don’t ignore them or feel embarrassed. Testing is a responsible, judgment-free step toward protecting your health and your partners.

If something feels off, getting tested can provide clarity, reassurance, and the right treatment—fast.

For individuals searching for STD testing in Manhattan or New York City, timely evaluation is especially important when symptoms like diarrhea or stomach pain follow sexual exposure.

Frequently Asked Questions

Can antibiotics for an STD upset your stomach or cause diarrhea?

Yes. Some STD antibiotics can cause temporary diarrhea or stomach upset. This usually starts after treatment begins and resolves once medication is finished.

Can you have an STD-related rectal infection without any bowel symptoms?

Yes. Many rectal STDs cause no symptoms at all, which is why routine screening is important.

Does diarrhea from an STD feel different from regular diarrhea?

Sometimes. It may involve rectal discomfort, mucus, or bleeding, but symptoms often overlap with common GI illnesses.

Can protected sex still lead to infections that cause diarrhea?

Yes. Condoms reduce risk but don’t fully prevent infections spread through oral–anal contact or skin-to-skin exposure.

Should partners be tested if diarrhea turns out to be STD-related?

Yes. Recent partners should be tested to prevent reinfection and further spread.

Disclaimer

This blog is for informational & educational purposes only and does not intend to substitute any professional medical advice or consultation. For any health-related concerns, please consult with your physician, or call 911.