Who should not take deworming tablets?

October 10, 2025 •

4 min read

While deworming tablets are generally safe and effective for treating parasitic infections in most adults and children, certain individuals must exercise caution. A person's health status, age, and existing medical conditions are critical factors in determining who should not take deworming tablets.

Quick Summary

A specific group of individuals must avoid deworming medication, including pregnant and breastfeeding women, children under two, and those with pre-existing medical conditions like liver disease or bone marrow suppression. Always consult a healthcare professional before use.

Key Points

Pregnant and Breastfeeding Women: These individuals should avoid deworming tablets due to potential harm to the fetus or infant.
Children Under Two Years: Children below the age of two should not take deworming tablets without explicit medical consultation.
Pre-existing Liver or Bone Marrow Conditions: Patients with liver disease or bone marrow suppression are at risk of serious complications and require careful medical supervision.
Hypersensitivity to Ingredients: A history of allergic reaction to the active ingredients (e.g., albendazole, mebendazole) is a strict contraindication.
Specific Drug Interactions: Some deworming medications interact negatively with other drugs, such as mebendazole and metronidazole.
Acute Illness or Fever: It is advisable to wait until a person has recovered from an acute illness or high fever before taking deworming medication.
Ocular Cysticercosis: Praziquantel is contraindicated in patients with this condition, as parasite destruction in the eye can cause damage.

Critical considerations before taking deworming medication

Before taking any medication, especially over-the-counter options like deworming tablets, understanding the contraindications is vital for preventing adverse health effects. The broad-spectrum anti-worm medications mebendazole and albendazole are common active ingredients but are not suitable for everyone. Certain populations are at a higher risk of complications and should always seek a doctor's advice before beginning treatment.

Pregnant and breastfeeding individuals

According to medical guidelines, pregnant and breastfeeding women are strongly advised against taking deworming medication.

Pregnancy: Deworming drugs, such as albendazole and ivermectin, are categorized as Pregnancy Category C, meaning animal studies have shown potential adverse effects on the fetus. Although some reviews suggest the risk might be lower, especially after the first trimester, official recommendations are to avoid them unless deemed absolutely necessary by a healthcare provider. Women planning a pregnancy are often advised to complete deworming treatments several months in advance.
Breastfeeding: The potential for active ingredients to pass into breast milk and harm the nursing baby is a primary concern. The risk versus the potential benefits must be carefully weighed and discussed with a doctor, as data on safety during breastfeeding is often limited.

Pediatric patients

The age of a child is a crucial factor in determining if they should take deworming medication. The dosage and appropriateness of the medication differ significantly based on age and weight.

Children under two years old: The consensus among health professionals is that deworming medication is not recommended for children under 2 years old without a doctor's consultation. This is because safety and efficacy are not well-established in this young age group. For infants and toddlers suspected of having a worm infection, a physician's guidance is mandatory.
Children under a specific weight: For some medications like ivermectin, specific weight limits exist. The CDC notes that the safety of ivermectin is unclear for children weighing less than 15 kg (33 lbs).

Individuals with pre-existing medical conditions

Patients with certain chronic or acute medical problems must avoid deworming tablets or use them only under strict medical supervision.

Liver disease: The liver metabolizes most deworming drugs, including albendazole and mebendazole. For patients with liver disease, dysfunction, or elevated liver enzymes, using these medications can increase the risk of serious side effects, including liver damage or failure. Monitoring liver enzymes during treatment is often necessary.
Bone marrow suppression: Conditions that cause bone marrow suppression can be worsened by deworming medication. The drugs can temporarily lower white blood cell and platelet counts, increasing the risk of infection or bleeding. This risk is particularly relevant for patients who have recently undergone chemotherapy.
Acute illness and high fever: Individuals with an acute illness, such as a high fever above 38°C, should postpone deworming until they have recovered.
Specific parasitic infections: In rare cases, treating certain parasitic infections with deworming tablets can be dangerous. For instance, in ocular cysticercosis, killing parasites in the eye with drugs like praziquantel can cause retinal damage.

People with drug allergies or sensitivities

Any history of a hypersensitivity or allergic reaction to the active ingredients (e.g., albendazole, mebendazole) or other components of a deworming tablet is a strict contraindication. Allergic reactions can range from hives and skin rash to severe, life-threatening anaphylaxis.

Individuals taking other medications

Drug interactions can occur when taking deworming tablets with other prescription or over-the-counter medicines. For example, mebendazole should not be taken with metronidazole, as this combination has been linked to a serious skin reaction. Other interactions are possible with certain medications for seizures (like carbamazepine) or stomach acid (cimetidine). Always provide a comprehensive list of all your medications and supplements to your doctor or pharmacist to screen for potential interactions.

Comparison of risks for different patient groups


Patient Group	Primary Risks	Key Recommendation
Pregnant Women	Potential harm to the fetus; not enough safety data, especially in the first trimester.	Avoid use; women of childbearing age should take a pregnancy test beforehand.
Breastfeeding Women	Possible drug transfer into breast milk, posing a risk to the infant.	Exercise caution; discuss with a doctor to weigh risks and benefits.
Children under 2	Safety and efficacy are not well-established; dosage is different and requires medical guidance.	Only use under a doctor's supervision for confirmed infections.
Liver Disease Patients	Increased risk of liver damage or failure due to drug metabolism issues.	Regular liver function monitoring required; caution is necessary.
Bone Marrow Suppression	Worsening of condition; risk of low blood cell counts, infection, and bleeding.	Require close monitoring of blood counts; extra vigilance for signs of infection.
Drug Allergies	Severe allergic reaction, including anaphylaxis.	Avoid completely if a hypersensitivity to ingredients is known.

Conclusion

While deworming tablets are a safe and necessary treatment for many, they are not a one-size-fits-all solution. Specific groups, including pregnant and breastfeeding individuals, young children, and those with certain health conditions like liver or bone marrow problems, face heightened risks. Hypersensitivity to ingredients and interactions with other medications are also critical factors. It is essential to consult a healthcare professional before taking any deworming medication to ensure it is safe and appropriate for your specific health situation. Self-treating without understanding these vital precautions can lead to serious health complications.

For more detailed information on specific medications like Albendazole, consult authoritative sources such as WebMD.

Additional Considerations

To ensure the safest use of deworming tablets, consider these points:

Acute illness: Postpone treatment if you are experiencing a high fever or an acute illness.
Retreatment: If a repeat dose is necessary, follow your doctor's instructions precisely and do not repeat treatment more frequently than recommended.
Full course: Always complete the full course of treatment as prescribed, even if symptoms improve.
Household treatment: For infections like pinworms, it may be necessary to treat all household members, but only if they fall outside the contraindicated groups.

By being aware of who should not take deworming tablets, individuals can protect themselves and their families from unnecessary health risks.

Frequently Asked Questions

No, pregnant women should avoid deworming medication, especially in the first trimester, due to potential risks to the unborn baby. It is important to consult a doctor for a proper risk assessment.

Generally, deworming tablets are not recommended for children under the age of two without specific guidance from a healthcare provider. Safety has not been fully established for this age group.

If you have liver disease, you should not take deworming tablets without medical supervision. The liver metabolizes the medication, and liver dysfunction increases the risk of serious side effects.

Certain medications can interact with deworming tablets. For instance, mebendazole should not be taken with metronidazole due to the risk of severe skin reactions. Always inform your doctor of all medicines you are taking.

Individuals with a known hypersensitivity or allergic reaction to the active ingredients (like albendazole or mebendazole) or other components of the tablet should avoid it completely.

No, it is advisable to postpone deworming treatment if you have an acute illness or a high fever (over 38°C) until you have recovered.

Breastfeeding women should exercise caution and consult a healthcare professional before taking deworming tablets, as the medication may pass into breast milk.

While some deworming tablets are available over-the-counter, it is highly recommended to consult a doctor or pharmacist, especially if you fall into any of the high-risk categories, to ensure safety and effectiveness.