Can You Have Worms Without Symptoms?

Yes. According to the CDC, many people with intestinal worms have no symptoms at all, especially when only a few worms are present, so it is possible to have worms and not know it. Pinworm, roundworm, whipworm, hookworm and Strongyloides can all go unnoticed, and Strongyloides can stay in the body for many years.

This page explains which worms commonly cause no symptoms, why a silent infection can still matter, and how clinicians check for worms when you feel fine. It is general education, not medical advice.

Why worms often cause no symptoms

For most intestinal worms, symptoms depend on how many worms are present. The CDC describes infections with only a few worms as light infections and says people with light infections usually have no symptoms. Heavy infections, with many worms, are the ones more likely to cause belly pain, diarrhea, blood loss and slow growth in children.

That means a person can carry a small number of worms for some time without noticing anything. It also means the absence of symptoms doesn't rule worms out if you have had a likely exposure, such as living in or traveling to an area where they are common.

Worm by worm: which ones stay silent

• Pinworm (Enterobius). In its overview for clinicians, the CDC says most people with pinworm have no symptoms or signs. When symptoms do appear, the usual one is itching around the anus. See what happens if pinworms go untreated.
• Roundworm (Ascaris). The CDC says some people with roundworm have few or no symptoms at all. Heavy infections are more common in children and can block the intestines. See roundworm in humans.
• Whipworm (Trichuris). The CDC says people with light whipworm infections usually have no signs or symptoms. Heavy infections can cause frequent, painful bowel movements with mucus, water and blood. See whipworm in humans.
• Hookworm. The CDC says some people with hookworm have few or no symptoms. When there are symptoms, the first is often an itchy rash where the larvae went through the skin; heavy infections can lead to tiredness and anemia. See hookworm in humans.
• Strongyloides. The CDC says most people infected with Strongyloides have no symptoms and may not know they are infected. See strongyloidiasis symptoms and treatment.

Can you have worms for years without knowing?

For most of these worms, a light infection can go unnoticed, but Strongyloides stands out. Its larvae can re-infect the same person from inside the gut or around the anus. The CDC Yellow Book, a guide for travel health clinicians, says that because of this autoinfection, a Strongyloides infection can last many years or even a lifetime. The CDC's overview for clinicians describes long-term (chronic) strongyloidiasis as generally causing no symptoms.

So a person who lived in, or spent time in, a warm, rural area where Strongyloides is found may carry it long after leaving, often without any symptoms.

Why a silent infection can still matter

No symptoms doesn't always mean no risk:

• Strongyloides and immune-weakening medicines. The CDC says strongyloidiasis can be severe or even life-threatening in people with immune disorders or people who take medicines that weaken the immune system, such as corticosteroids (steroids). The CDC's clinical overview notes that the most severe form is most often seen in people whose infection had caused no symptoms before they were given high-dose steroids. If you have lived in or traveled to a higher-risk area and are about to start steroids or another immune-weakening medicine, tell the clinician who prescribes it.
• Spread to others. Pinworm passes easily between people who live together. The CDC advises household members and other close contacts to follow good hygiene, including handwashing, bathing and washing clothes and bedding, and notes that repeat infections are common in childcare centers and schools. See are worms contagious?
• Heavy or long-lasting infections. The CDC links heavy hookworm and whipworm infections to blood loss and anemia, and heavy infections in children to slower growth. Our guide to whether worms can cause anemia explains more.

How clinicians check for worms when you feel fine

Because symptoms are an unreliable guide, the right test depends on which worm is suspected and on your history, such as travel, where you have lived and who in your household has symptoms:

• Stool test. The CDC says roundworm, whipworm and hookworm are found by checking a stool sample for eggs under a microscope. For Strongyloides, the CDC notes that standard stool exams often miss it and that several samples may be needed. See stool test for parasites.
• Blood test. The CDC says Strongyloides can be identified with a blood test as well as with a stool exam. There is no blood test for pinworm. See can a blood test detect parasites?
• Tape test. For pinworm, the CDC says the most common test is the tape test, done first thing in the morning. See the pinworm tape test.

If you're not sure who to ask, see what kind of doctor treats parasites. If you traveled recently, our page on parasites from traveling covers what to tell your clinician.

Getting a prescription through Get It Prescribed

Get It Prescribed is a telehealth service for adults. It does not perform lab tests. A licensed provider reviews a written health assessment, including any test results you already have, and decides whether mebendazole or ivermectin is appropriate for a labeled use. Mebendazole's labeled uses are pinworm, whipworm, roundworm and hookworm; ivermectin's are intestinal strongyloidiasis and onchocerciasis. No prescription is guaranteed, and the provider may recommend testing or an in-person visit instead. How it works shows each step.

The medicines dispensed through Get It Prescribed are compounded preparations made by a licensed compounding pharmacy. They are not FDA-approved, the FDA has not reviewed them for safety, effectiveness or quality, and they are not generics of, or substitutes for, the brand-name products.

The cost is a one-time $50 provider consultation fee, plus $3.00 per ivermectin tablet or $3.50 per mebendazole capsule if a prescription is issued, with the quantity decided by the provider. The service is available in all 50 states and the District of Columbia; some states require a live phone or video visit.

This article is general education, not medical advice. It does not replace an evaluation by a licensed clinician who knows your history.

Related questions

Can you have worms for years without knowing?

It is possible, especially with Strongyloides. The CDC Yellow Book says it can re-infect the same person from inside the body, so an infection can last many years or a lifetime, and the CDC says most people with it have no symptoms.

Can you have pinworms and not know it?

Yes. The CDC's overview for clinicians says most people with pinworm have no symptoms or signs. When there are symptoms, the usual one is itching around the anus.

Can I spread worms if I don't have symptoms?

Pinworm spreads easily between people who live together, which is why the CDC advises everyone in the household to follow good hygiene. The CDC says roundworm, whipworm and hookworm spread a different way, through soil or water contaminated with human stool.

Should I get tested for worms if I feel fine?

Ask a clinician, especially if you have lived in or traveled to an area where worms are common, someone in your home has pinworm, or you are about to start steroids or another medicine that weakens the immune system.

Will a normal blood count rule out worms?

No. The CDC notes that up to three in four people with long-term Strongyloides have a mildly raised eosinophil count (a type of white blood cell), so a normal count doesn't rule it out, and there is no blood test for pinworm. Many intestinal worms are found with a stool test instead. Your clinician decides which test fits your history.

Sources

• CDC: About Soil-transmitted Helminths — light infections usually cause no symptoms; heavy infections cause belly pain, diarrhea and blood loss; stool test for diagnosis.
• CDC: Clinical Overview of Pinworm Infection — most people have no symptoms; the tape test; no blood test; hygiene advice for household contacts.
• CDC: About Ascariasis — few or no symptoms; heavy infections in children.
• CDC: About Whipworms — light infections usually cause no symptoms; stool exam for diagnosis.
• CDC: About Hookworm — few or no symptoms; rash where larvae enter; anemia with heavy infection.
• CDC: About Strongyloides — most people have no symptoms and may not know they're infected; severe illness with immune-weakening medicines; blood or stool test.
• CDC: Clinical Overview of Strongyloides — chronic infection is generally without symptoms; severe forms linked to high-dose steroids; up to three in four have mild eosinophilia; several stool exams may be needed.
• CDC Yellow Book: Post-Travel Parasitic Disease — Strongyloides infection can last many years or be lifelong because of autoinfection.
• DailyMed: mebendazole chewable tablet prescribing information — labeled uses: pinworm, whipworm, roundworm and hookworm.
• DailyMed: ivermectin tablet prescribing information — labeled uses: intestinal strongyloidiasis and onchocerciasis.
• FDA: Compounding and the FDA — Questions and Answers — what compounded preparations are and how they are regulated.