Herb & supplement monograph

Water Hemlock Drug Interactions, Uses, Safety & More

Medically reviewed by ·Updated July 2026
What is this page for?

First and foremost: how Water Hemlock interacts with medications. The heart of this page is the interaction list — every drug Water Hemlock is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Water Hemlock is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Water Hemlock Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Water Hemlock drug interaction appears low for most people, with one exception worth knowing about. Only a single interaction is documented, it is rated moderate rather than major, and no major interactions are known.

Interactions deserving the most attention

The one combination that stands out involves lithium, a mood-stabilizing medicine with a narrow safety margin where even small changes in blood levels matter. Water hemlock is thought to act as a diuretic, meaning it may make the body pass more urine, and that could slow how the body clears lithium and push lithium levels higher. Anyone taking lithium should treat this pairing with real caution, since a rise in lithium levels can be meaningful.

What the rest of the list means

This concern is based on the plant's suspected diuretic effect rather than on studies directly measuring lithium levels in people, so the interaction is predicted rather than proven. Beyond lithium, no other medication interactions have been documented for water hemlock, which is unusual among herbal ingredients and keeps its interaction picture simple.

Check your medications against Water Hemlock

Based on HelloPharmacist’s Water Hemlock interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Water Hemlock

1 medication has a known interaction with Water Hemlock, graded by severity. Select any drug for the full evidence-based detail.

2,830 drugs
Lithium Carbonate (prescription Drug)Eskalith, Lithium Carbonate› "phentolamineOraVerse, Rogitine, Ryzumvi› 6-mercaptopurinePurinethol› Ado-trastuzumab EmtansineKadcyla› AbacavirZiagen› Abacavir Sulfate, Dolutegravir, LamivudineTriumeq› Abacavir, LamivudineEpzicom› AbaloparatideTymlos› AbametapirXeglyze› AbarelixPlenaxis› AbciximabReoPro› AbemaciclibVerzenio› Abiraterone› Abiraterone AcetateYonsa, Zytiga› AbrocitinibCibinqo› AcalabrutinibCalquence› AcamprosateCampral› AcarboseGlucobay, Prandase, Precose› AcebutololRhotral, Sectral› AcenocoumarolSintrom› AcepromazineAtravet› AcetaminophenChildren's Tylenol, Children's Tylenol Meltaways, Tylenol, Tylenol Ex Strength› Acetaminophen, AspirinGemnisyn› Acetaminophen, Aspirin, CaffeineExcedrin, Excedrin Extra Strength, Excedrin Migraine› Acetaminophen, Brompheniramine, PhenylpropanolamineDimetapp Cold and Flu› Acetaminophen, ButalbitalAxocet, Bancap, Bucet, Butex Forte, Esgic CF, Orbivan CF +5 more› Acetaminophen, Butalbital, CaffeineEsgic, Esgic Plus, Fiogesic, Fioricet, Repan, Tecnal +1 more› Acetaminophen, Butalbital, Caffeine, CodeineEsgic with Codeine, Fioricet w/ Codeine› Acetaminophen, Butalbital, CodeineBancap w/ Codeine› Acetaminophen, Butalbital, Codeine PhosphatePhrenilin #3›
Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

  • Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
  • Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
  • Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
  • No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

  • Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
  • Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
  • Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

  • Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
  • Each drug listed above links to the full report for that exact Water Hemlock combination — clinical detail, likelihood, evidence level, and citations.
  • Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.
The big picture

The kinds of drugs Water Hemlock affects

Every type of medication (drug category) Water Hemlock is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 1 drug category Water Hemlock interacts with
Lithium
Lithium

Water hemlock is thought to have diuretic properties. Theoretically, due to these potential diuretic effects, water hemlock might reduce excretion and increase levels of lithium. The dose of lithium might need to be decreased.

Likelihood Probable Evidence D
Monograph

Water Hemlock: Uses, Safety & Side Effects

Medically reviewed by · Reviewed July 2026 ·
The bottom line

Water hemlock is one of the most poisonous plants in North America and is NOT a safe dietary supplement or herbal remedy. Even small amounts can cause violent seizures and death. Never eat, brew, or take any part of this plant, and seek emergency care immediately if exposure is suspected.

Scientific name
Cicuta maculata
Family
Apiaceae
Part used
None — this is a toxic plant, not a usable supplement (roots are the most poisonous part)
Common forms
Not used as a supplement; sometimes mistaken for edible wild plants
People commonly use it for
  • Historically misused in folk practice (not recommended)
  • Sometimes confused with edible wild carrots or parsnips
  • No safe medicinal use

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance
OverallBest avoided

Water hemlock is deadly poisonous and should never be consumed.

PregnancyUnsafe

When used orally or topically. Water hemlock is toxic; avoid using.

Read the full pregnancy detail
BreastfeedingUnsafe

When used orally or topically. Water hemlock is toxic; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Water hemlock (often Cicuta maculata) is a flowering plant in the carrot and parsley family. It grows in wet areas like marshes, ditches, stream banks, and wet meadows across much of North America. It has clusters of small white flowers and a hollow, sometimes streaked or spotted stem.

Despite being grouped here, water hemlock is not a dietary supplement or herbal medicine. It is widely considered one of the most toxic plants in North America. People are usually harmed by accident — most often by mistaking it for edible wild plants such as wild parsnip, wild carrot, or water parsnip.

This monograph exists mainly to warn against any use of this plant, not to describe a benefit.

Uses & effectiveness

There are no proven or safe medicinal uses for water hemlock. Any historical or folk references to it are not supported by evidence, and the risk of death far outweighs any imagined benefit.

The most important practical point is recognition and avoidance. Foragers sometimes confuse water hemlock with safe wild plants, which has led to severe poisonings and deaths. There is no preparation, dose, or method that makes this plant safe to take.

How it works

The main toxic compound in water hemlock is cicutoxin, which is concentrated in the roots but found throughout the plant. Cicutoxin acts on the central nervous system.

Based on what scientists understand, cicutoxin interferes with a calming brain signal pathway (it blocks GABA-related activity). This causes the nervous system to become dangerously overactive, leading to violent muscle spasms and seizures. These effects can begin within minutes of swallowing the plant.

Safety & precautions

Water hemlock is deadly and should never be eaten, brewed into tea, juiced, or handled carelessly. Even tasting a small piece of the root can be fatal. Children and pets are also at risk.

People who forage for wild plants should be especially cautious, because water hemlock looks similar to several edible plants. When in doubt, do not pick or eat any wild plant in the carrot family.

Pregnancy and breastfeeding: This plant is extremely toxic and must be avoided completely. There is no safe amount during pregnancy, while breastfeeding, or at any other time.

If you suspect someone has eaten water hemlock, call emergency services (911 in the U.S.) or your local poison control center right away. Do not wait for symptoms to appear.

Side effects

Water hemlock poisoning is a medical emergency. Symptoms often appear quickly — sometimes within 15 to 60 minutes — and may include:

  • Nausea, vomiting, and abdominal pain
  • Excess salivation and sweating
  • Tremors and muscle twitching
  • Severe, repeated seizures
  • Confusion or loss of consciousness
  • Trouble breathing, dangerous heart rhythm changes, and death

Because of the violent seizures, people may also suffer injuries, breakdown of muscle tissue, and kidney problems. Survival often depends on how quickly emergency treatment is started.

Water Hemlock: Reported Adverse Effects

Documented safety reports on Water Hemlock from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

Water hemlock is a known highly toxic plant and causes a variety of symptoms including vomiting, acute renal failure, marked metabolic acidosis, seizures and convulsions, or unconsciousness that may lead to death.

  1. Applefeld JJ, Caplan ES. A case of water hemlock poisoning. JACEP 1979;8:401-3.
  2. Rizzi, D., Basile, C., Di Maggio, A., Sebastio, A., Introna, F., Jr., Rizzi, R., Scatizzi, A., De Marco, S., and Smialek, J. E. Clinical spectrum of accidental hemlock poisoning: neurotoxic manifestations, rhabdomyolysis and acute tubular necrosis. Nephr
  3. Carlton BE, Tufts E, Girard DE. Water hemlock poisoning complicated by rhabdomyolysis and renal failure. Clin Toxicol 1979;14:87-92.
  4. Knutsen OH, Paszkowski P. New aspects in the treatment of water hemlock poisoning. J Toxicol Clin Toxicol 1984;22:157-66.
  5. Starreveld E, Hope E. Cicutoxin poisoning (water hemlock). Neurol 1975;25:730-4.
  6. Landers, D., Seppi, K., and Blauer, W. Seizures and death on a white river float trip. Report of water hemlock poisoning. West J.Med. 1985;142(5):637-640.
  7. Heath, K. B. A fatal case of apparent water hemlock poisoning. Vet.Hum.Toxicol. 2001;43(1):35-36.
Reports by condition
Epilepsy Neurologic/CNS

According to case reports, oral ingestion may cause an explosive illness with seizures and convulsions, neurologic lethargy, or unconsciousness that may lead to death.

  1. Rizzi, D., Basile, C., Di Maggio, A., Sebastio, A., Introna, F., Jr., Rizzi, R., Scatizzi, A., De Marco, S., and Smialek, J. E. Clinical spectrum of accidental hemlock poisoning: neurotoxic manifestations, rhabdomyolysis and acute tubular necrosis. Nephr
  2. Landers, D., Seppi, K., and Blauer, W. Seizures and death on a white river float trip. Report of water hemlock poisoning. West J.Med. 1985;142(5):637-640.
  3. Knutsen OH, Paszkowski P. New aspects in the treatment of water hemlock poisoning. J Toxicol Clin Toxicol 1984;22:157-66.
  4. Starreveld E, Hope E. Cicutoxin poisoning (water hemlock). Neurol 1975;25:730-4.
  5. Applefeld JJ, Caplan ES. A case of water hemlock poisoning. JACEP 1979;8:401-3.
  6. Heath, K. B. A fatal case of apparent water hemlock poisoning. Vet.Hum.Toxicol. 2001;43(1):35-36.
Hypotension Cardiovascular

According to case reports, oral ingestion may cause an explosive illness with orthostatic hypotension or tachycardia.

  1. Applefeld JJ, Caplan ES. A case of water hemlock poisoning. JACEP 1979;8:401-3.
Muscle breakdown Musculoskeletal

According to case reports, oral ingestion may cause an explosive illness with rhabdomyolysis.

  1. Rizzi, D., Basile, C., Di Maggio, A., Sebastio, A., Introna, F., Jr., Rizzi, R., Scatizzi, A., De Marco, S., and Smialek, J. E. Clinical spectrum of accidental hemlock poisoning: neurotoxic manifestations, rhabdomyolysis and acute tubular necrosis. Nephr
  2. Carlton BE, Tufts E, Girard DE. Water hemlock poisoning complicated by rhabdomyolysis and renal failure. Clin Toxicol 1979;14:87-92.
Muscle breakdown Renal

According to case reports, oral ingestion may cause an explosive illness with rhabdomyolysis, marked metabolic acidosis, or acute renal failure.

  1. Rizzi, D., Basile, C., Di Maggio, A., Sebastio, A., Introna, F., Jr., Rizzi, R., Scatizzi, A., De Marco, S., and Smialek, J. E. Clinical spectrum of accidental hemlock poisoning: neurotoxic manifestations, rhabdomyolysis and acute tubular necrosis. Nephr
  2. Carlton BE, Tufts E, Girard DE. Water hemlock poisoning complicated by rhabdomyolysis and renal failure. Clin Toxicol 1979;14:87-92.
  3. Knutsen OH, Paszkowski P. New aspects in the treatment of water hemlock poisoning. J Toxicol Clin Toxicol 1984;22:157-66.
  4. Starreveld E, Hope E. Cicutoxin poisoning (water hemlock). Neurol 1975;25:730-4.
Nausea and vomiting Gastrointestinal

According to case reports, oral ingestion causes an explosive illness with nausea, vomiting, or abdominal cramps.

  1. Applefeld JJ, Caplan ES. A case of water hemlock poisoning. JACEP 1979;8:401-3.
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

Adverse-effects data: Natural Medicines, Therapeutic Research Center

Dosing

There is no safe dose of water hemlock. It is not a supplement and should never be taken in any amount or form.

If you see a product or remedy claiming to contain water hemlock, do not use it, and talk to a pharmacist or doctor. The only appropriate action with this plant is avoidance and, in case of exposure, emergency care.

Pregnancy & Breastfeeding

Water Hemlock & Pregnancy

Unsafe

When used orally or topically. Water hemlock is toxic; avoid using.

  1. Knutsen OH, Paszkowski P. New aspects in the treatment of water hemlock poisoning. J Toxicol Clin Toxicol 1984;22:157-66.
  2. Anon. Water hemlock poisoning - Maine, 1992. MMWR Morb Mortal Wkly Rep 1994;43:229-31. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/00026056.htm.

Water Hemlock & Breastfeeding

Unsafe

When used orally or topically. Water hemlock is toxic; avoid using.

  1. Knutsen OH, Paszkowski P. New aspects in the treatment of water hemlock poisoning. J Toxicol Clin Toxicol 1984;22:157-66.
  2. Anon. Water hemlock poisoning - Maine, 1992. MMWR Morb Mortal Wkly Rep 1994;43:229-31. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/00026056.htm.
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

© 2026 Therapeutic Research Center

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 8 references that drive our Water Hemlock monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Starreveld E, Hope E. Cicutoxin poisoning (water hemlock). Neurol 1975;25:730-4. PubMed
  2. Knutsen OH, Paszkowski P. New aspects in the treatment of water hemlock poisoning. J Toxicol Clin Toxicol 1984;22:157-66. PubMed
  3. Anon. Water hemlock poisoning - Maine, 1992. MMWR Morb Mortal Wkly Rep 1994;43:229-31. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/00026056.htm.
  4. Applefeld JJ, Caplan ES. A case of water hemlock poisoning. JACEP 1979;8:401-3. PubMed
  5. Carlton BE, Tufts E, Girard DE. Water hemlock poisoning complicated by rhabdomyolysis and renal failure. Clin Toxicol 1979;14:87-92. PubMed
  6. Rizzi, D., Basile, C., Di Maggio, A., Sebastio, A., Introna, F., Jr., Rizzi, R., Scatizzi, A., De Marco, S., and Smialek, J. E. Clinical spectrum of accidental hemlock poisoning: neurotoxic manifestations, rhabdomyolysis and acute tubular necrosis. Nephr PubMed
  7. Heath, K. B. A fatal case of apparent water hemlock poisoning. Vet.Hum.Toxicol. 2001;43(1):35-36.
  8. Landers, D., Seppi, K., and Blauer, W. Seizures and death on a white river float trip. Report of water hemlock poisoning. West J.Med. 1985;142(5):637-640. DOI
Keep reading

This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Pharmacist Counseling Corner

Water Hemlock: Common Questions

Does Water Hemlock interact with prescription medications?
Yes. We list 1 medication with a known interaction with Water Hemlock. Use the checker above to see how Water Hemlock interacts with a specific drug.
How are Water Hemlock interactions rated?
Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.
Is it safe to take Water Hemlock with my medications?
It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.
Where does this Water Hemlock interaction information come from?
Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.
Is Water Hemlock safe to take as a supplement?
No. Water Hemlock is one of the most poisonous plants in North America, and even small amounts can cause deadly seizures. It should never be taken as a supplement or remedy.
What happens if someone eats Water Hemlock?
Poisoning can cause vomiting, tremors, and violent seizures within minutes, and can be fatal. This is a medical emergency — call 911 or poison control immediately and do not wait for symptoms.
How can I tell Water Hemlock apart from edible wild plants?
It can be very hard to tell apart from plants like wild carrot or water parsnip, which is why poisonings happen. If you are not 100% certain, do not pick or eat any wild plant in the carrot family.
Is Water Hemlock the same as poison hemlock?
No, they are different plants, though both are highly toxic. Water Hemlock (Cicuta species) contains cicutoxin, while poison hemlock (Conium maculatum) contains coniine. Neither should ever be consumed.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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