Understanding When Should I Not Eat Rhubarb? A Guide to Safe Consumption

October 22, 2025 •

4 min read

Overconsumption of rhubarb leaves has historically led to poisoning due to high levels of oxalic acid. This is a crucial detail for understanding when should I not eat rhubarb, as safety depends on knowing which parts are edible, how it should be prepared, and if certain health conditions apply.

Quick Summary

This nutritional guide details the specific circumstances under which one should avoid rhubarb consumption, focusing on its toxic leaves and the health risks associated with the high oxalate content in its stalks for certain individuals. It covers risks for those with kidney conditions, on specific medications, and for pregnant individuals, while emphasizing safe preparation.

Key Points

Avoid Rhubarb Leaves: Rhubarb leaves are highly toxic due to their high oxalic acid content and must never be consumed.
Be Cautious with Kidney Issues: Individuals with a history of kidney stones or kidney disease should avoid rhubarb due to its high oxalate content.
Check for Medication Interactions: Rhubarb can interfere with blood-thinners (warfarin), laxatives, and diuretics, so consult a doctor if taking these medications.
Consume Cooked Stalks Safely: Cooking rhubarb reduces its oxalate content, making the stalks safer to eat, especially when paired with calcium-rich ingredients.
Inspect for Frost Damage: Discard any rhubarb stalks that have been damaged by a hard frost, as this can increase their toxicity.

The Poisonous Part of Rhubarb: The Leaves

The most critical and widely known rule of rhubarb consumption is to never eat the leaves. These large, green leaves contain dangerously high concentrations of oxalic acid, a naturally occurring compound that is toxic to humans and animals. While the edible stalks contain a much lower, safe concentration, the leaves are another story entirely. Ingesting rhubarb leaves can lead to a variety of severe symptoms, and in large enough quantities, can even be fatal, as was tragically discovered during World War I food shortages.

Symptoms of rhubarb leaf poisoning can include:

Burning sensation in the mouth and throat
Nausea, vomiting, and diarrhea
Stomach pain and weakness
Difficulty breathing
Blisters in the mouth and throat
In severe cases, kidney damage, seizures, or coma

When harvesting or preparing rhubarb, it is essential to trim the leaves off completely and discard them safely, away from pets and children who might accidentally ingest them. The leaves should not be added to compost used for edible crops, as the toxins could persist.

Health Conditions That Require Avoiding Rhubarb

For most healthy individuals, consuming cooked rhubarb stalks in moderation is perfectly safe. However, due to its oxalic acid content, certain health conditions require caution or complete avoidance.

Kidney stones and kidney disease

Rhubarb is rich in calcium oxalate, the compound that makes up the most common type of kidney stone. For individuals with a history of calcium oxalate kidney stones or those with kidney disease, consuming rhubarb is a significant risk. The body converts oxalate into crystals that can accumulate and form stones, and in excess, can damage the kidneys. Even for those without a history, excessive consumption can be problematic, especially with raw rhubarb. Cooking rhubarb with a calcium source like milk can help reduce the soluble oxalate content by binding it before it's absorbed.

Gastrointestinal conditions

Rhubarb can have a laxative effect, particularly when taken in concentrated medicinal forms. For those with inflammatory bowel conditions like Crohn's disease, colitis, or irritable bowel syndrome (IBS), or unexplained stomach pain, rhubarb can exacerbate symptoms. It should also be avoided by those with a bowel obstruction.

Liver problems

Rhubarb can worsen liver function in those who already have liver problems. While some studies show traditional uses for liver support, individuals with pre-existing conditions should consult a doctor before consuming rhubarb, particularly in medicinal amounts.

Medication Interactions

Beyond specific health conditions, rhubarb can interact with certain medications, making its consumption inadvisable for some individuals.

Blood-thinning medication (warfarin)

Rhubarb is a rich source of vitamin K, a nutrient essential for blood clotting. This high vitamin K content can interfere with the effectiveness of blood-thinning medications like warfarin, potentially increasing the risk of dangerous bleeding.

Stimulant laxatives

Since rhubarb itself acts as a stimulant laxative, combining it with other laxatives can be dangerous. It could lead to excessive bowel movements, dehydration, and a loss of essential minerals, such as potassium.

Diuretics ('water pills')

Similar to laxatives, diuretics already cause a loss of potassium. The laxative effect of rhubarb can further deplete the body's potassium levels, which can be dangerous.

Drugs that can harm the kidneys or liver

For those taking medications that are metabolized by the kidneys or liver, adding rhubarb to the diet can increase the risk of damage. It is crucial to discuss any dietary changes with a healthcare provider if taking such medication.

Rhubarb and Pregnancy

The safety of consuming rhubarb during pregnancy is often debated, with conflicting advice available. While many experts agree that cooked rhubarb stalks are safe in moderation during pregnancy, some caution is warranted due to the oxalate content and potential laxative effects. Some sources suggest avoiding concentrated rhubarb extracts entirely, while others advise against it for toddlers and breastfeeding mothers as well. The best approach is always to consult a healthcare provider for personalized guidance.

A Comparison of Rhubarb's Risks and Proper Preparation


Feature	Risks and Warnings	Safe Preparation and Consumption
Leaves	Contain toxic oxalic acid. Can cause severe illness or death if ingested.	Always remove and discard leaves completely before cooking.
Stalks	Contain lower levels of oxalates. Risks increase with high-oxalate varieties, excessive consumption, or for those with kidney issues. Can have a laxative effect.	Cooked stalks are safest. Cooking reduces oxalate levels. Use in moderation.
Freezing/Frost Damage	Freeze-damaged stalks may lead to higher oxalate concentration.	Discard mushy, damaged stalks after a hard freeze. Use only healthy, firm stalks.
Cooking	Minimal risk if only stalks are used.	Cooking reduces oxalate content. Cooking with a calcium source can further reduce oxalate levels.
Raw Consumption	Tarter taste due to oxalates. Highest oxalate levels are in uncooked stalks.	Consume raw only in very small amounts, and only if you don't have kidney stone susceptibility.

Conclusion

For most people, rhubarb is a delicious and nutritious vegetable, best enjoyed cooked and in moderation. However, knowing when should I not eat rhubarb is crucial for preventing illness and managing certain health conditions. The most important rule is to avoid the toxic leaves entirely. Beyond that, individuals with kidney issues, specific gastrointestinal problems, liver conditions, or who are taking certain medications should be cautious or avoid rhubarb altogether. Finally, pregnant or breastfeeding individuals should seek professional medical advice before adding rhubarb to their diet. By following these guidelines, you can ensure a safe and healthy culinary experience.

Learn more about how dietary choices impact health from reliable sources like the National Kidney Foundation.

Frequently Asked Questions

Yes, the large, green leaves of the rhubarb plant are poisonous. They contain very high concentrations of oxalic acid, which is toxic to both humans and animals.

People with a history of kidney stones or kidney disease, those with inflammatory gastrointestinal conditions, individuals with liver problems, and those taking certain medications like warfarin or diuretics should avoid rhubarb.

While cooked rhubarb stalks in moderation are generally considered safe, some sources advise caution due to the oxalate content and potential laxative effects. It's best to consult a healthcare provider for personalized advice.

Accidental ingestion, especially in small amounts, may cause mild symptoms like stomach upset. However, it is crucial to contact a local poison control center immediately, as serious poisoning can cause severe gastrointestinal distress, difficulty breathing, and in rare cases, kidney damage.

Cooking does not make rhubarb leaves safe to eat. However, for the edible stalks, cooking can reduce the levels of oxalic acid. It is always important to remove and discard the toxic leaves before cooking.

It is not recommended to eat rhubarb stalks after a hard frost. A freeze can damage the plant, and some sources suggest this can cause the toxic oxalic acid from the leaves to migrate into the stalks. It is safest to discard any mushy or damaged stalks.

Yes, rhubarb leaves are toxic to pets, including cats and dogs. Pet owners should ensure that rhubarb leaves are not left where animals can chew them and seek veterinary care if ingestion is suspected.