Comfrey Dosage for Horses: Dosage Chart, Calculator & Safety Guide Before You Feed a Single Scoop

Written & Reviewed By: Medshorse Team
Last Updated: October 2026

Comfrey has been fed to horses for generations, usually with the hope of supporting bones, tendons and sore tissue. The real question is how much is too much. Comfrey dosage for horses is not a simple “more is better” matter, because the plant carries natural liver toxins that build up over time. This guide gives you the label based amounts, a calculator and the safety limits that matter.

Quick answer: Hilton Herbs, a UK herbal brand, lists 20 to 30 grams of dried comfrey leaf per day for horses, ideally split across two feeds. Its 1:3 tincture is listed at 10 to 20 ml per day. Use comfrey for short courses only, and speak to your vet first.

Disclaimer: This article is for general education and is not veterinary advice. Product and brand names mentioned, including Hilton Herbs, Equine Herbals, Feedmark and Mad Barn, belong to their respective owners, and MedsHorse is not affiliated with them. Always follow your veterinarian’s instructions and the current product label.

What Is Comfrey and Why Do Horse Owners Feed It?

Comfrey (Symphytum officinale) is a leafy herb in the borage family. It is also called knitbone, a nickname that explains its reputation. Suppliers such as Equine Herbals describe it as rich in mucilage and allantoin, and it is popular for supporting the healing of damaged tissue such as broken bones and tendons.

That reputation comes from tradition, not from controlled horse trials. We found no published, weight based comfrey dose for horses backed by clinical studies. Every dose in this article comes from supplier labels, not from a veterinary drug monograph.

Nutritionally, comfrey at label amounts is a herb dose, not a feed. The Mad Barn Feed Bank lists one commercial comfrey leaf product at about 15.6 percent crude protein on a dry matter basis, with 90 percent dry matter.

At 20 to 30 g a day, that works out to roughly 2.8 to 4.2 g of protein. That is a small amount next to a horse’s hay.

Comfrey Dosage Chart for Horses

Here are the typical amounts printed by equine herb suppliers. Always follow the label on your own product, because strength varies between brands.

Product form	Typical label amount for a horse	How it is given	Source
Dried cut leaf	20 to 30 g per day	Add to feed, ideally split across two feeds	Hilton Herbs Comfrey Leaf
Tincture, 1:3 at 25%	10 to 20 ml per day	Add to feed, split if possible	Hilton Herbs Comfrey Tincture
Liquid herbal product	10 to 20 ml, twice daily	Two doses per day	Equine Herbals Comfrey Leaf
Scoop based leaf product	4 scoops per day (about 24 g)	Introduce gradually, split across feeds	Feedmark MeadowBlend Comfrey

Notice that the liquid products do not match. Equine Herbals lists 10 to 20 ml of its liquid product twice daily for all horses, while Hilton Herbs lists 10 to 20 ml in total per day for its tincture. The strengths and extraction methods differ, so never swap one brand’s volume for another’s.

Does Body Weight Change the Comfrey Dose?

Not in the way you might expect. The labels above give a flat amount for “horses,” not a milligram per kilogram figure. We found no verified formula for scaling comfrey up or down by weight.

For context, 20 to 30 g for a 500 kg horse equals about 0.004 to 0.006 percent of body weight. One veterinary reference notes that horses generally need to eat roughly 2 to 5 percent of their body weight in pyrrolizidine alkaloid plants before liver disease develops, though toxicity builds up over a lifetime.

That figure is a general estimate for PA plants, not a proven safe ceiling for comfrey, so label discipline still matters.

Ponies, miniatures and foals are the gap. Label doses are written for average sized horses, and no one has published a reliable scaled down amount. If your animal is small, ask your vet and do not guess.

Comfrey Dosage Calculator

Enter your horse’s weight and your product type to see the label range turned into feeds, scoops and a 30 day total. The calculator deliberately refuses to produce numbers for small animals.

Dried Leaf vs Tincture vs Fresh Comfrey

Dried leaf is the easiest form to measure accurately. You can weigh it, so you always know what your horse received. Choose a leaf only product, not one containing root. Veterinary references note that comfrey’s pyrrolizidine alkaloids are concentrated mainly in the roots, though the leaves carry them too.

Tincture is simple to dose with a syringe. It is an alcohol and water extract, so strength depends on the extraction ratio. Hilton Herbs’ version is 1:3 at 25 percent alcohol. Check the ratio on any other brand before comparing doses.

Fresh garden comfrey is the hardest to dose. Alkaloid content varies with the plant part, season, species and natural variation. You cannot see or measure that variation at the feed bucket, so a “handful” is a real unknown.

Poultices and compresses are a separate use. Product instructions differ, so follow your own label. Feedmark, for example, says to leave its poultice in place for no more than 8 hours and wait at least 8 hours before reapplying. Ask your vet before applying comfrey to any wound.

Form	Easiest to measure	Strength consistency	Best for
Dried leaf	Yes, by weight	Good, if from a reputable supplier	Daily feeding for a short course
Tincture	Yes, by syringe	Depends on extraction ratio	Owners who want small volumes
Fresh leaf	No	Poor	Not recommended for internal use
Poultice or compress	Not applicable	Varies by product	Topical use under vet guidance

Why Comfrey Dosage for Horses Needs Limits: The Liver Risk

This is the part many product pages skip. Comfrey contains pyrrolizidine alkaloids, or PAs, which the horse’s liver converts into harmful compounds. These alkaloids have been identified in the leaves and roots of both common and Russian comfrey, and they damage the liver.

Horses and cattle are generally the most severely affected, while sheep and goats are quite resistant.

The danger is that damage builds quietly. Horses can lose more than 80 percent of liver function by the time clinical signs appear. Once liver failure signs show, the damage is severe and irreversible, and the outlook is generally very poor.

Drying does not make comfrey safe. Research presented at the UC Davis alfalfa symposium notes that PAs resist heat and stay toxic in dried plant material.

Safety fact	What the sources say
PAs identified in comfrey	At least eight
Highest concentration	Root, roughly 0.3 to 0.4 percent
Liver function lost before signs appear	More than 80 percent
Effect of drying or heat	PAs persist
Most sensitive livestock	Horses and cattle

The evidence is not entirely one sided. Feedipedia notes that Russian comfrey is considered a toxic plant, yet feeding trials with it did not report toxicity problems.

Richters Herbs points out that herbalists cite centuries of animals eating the leaf, but that studies show PAs, especially from the root, can accumulate and harm the liver. Its advice is to use comfrey for specific conditions rather than daily.

For people, the UK Committee on Toxicity advised against eating comfrey root and leaves in its 1992 review. That advice was written for humans, but it shows how seriously regulators take the plant.

You can read the full Committee on Toxicity PA statement, and the IVIS poisonous plants guide covers horse specific effects.

How Long Can You Feed Comfrey to a Horse?

Keep it to a short course. Hilton Herbs says to allow up to one month to see benefits. Feedmark states that comfrey should not be fed for more than one month, and that it is not suitable for pregnant mares.

We could not verify a standard rest period between courses. Ask your vet how long to wait before any repeat course, and whether liver blood tests make sense before and after.

Who Should Not Get Comfrey

Skip comfrey, or speak to your vet before even considering it, in these cases:

• Pregnant mares. Feedmark lists comfrey as unsuitable for pregnant mares.
• Horses with known or suspected liver disease. The liver is the organ comfrey’s toxins target.
• Foals, ponies and miniatures. Label doses were not written for them.
• Horses on long term anti-inflammatory medication. The University of Kentucky notes that drugs such as phenylbutazone and flunixin can themselves damage the liver, especially at high doses, over long periods, or with existing conditions. Adding comfrey adds to the liver’s workload. If your horse is on bute, see our guide to bute dosage for horses.
• Horses fed hay from weedy fields. Comfrey is not the only PA source. Horses often fail to notice PA plants mixed into hay, and repeated ingestion of contaminated hay is one of the most frequent ways horses are poisoned.

Signs of Liver Trouble to Watch For

Early signs are easy to miss. Appetite loss is the most commonly listed one, and your vet may confirm trouble through liver enzyme tests. Other signs can include weight loss, dullness, yellow tinged gums and behavior changes.

Comfrey and Competition Rules

If you compete, check the rules before feeding anything herbal. The FEI forbids herbal or natural products used to calm or energize a horse. Cross contamination between herbal products is possible, and an accidental positive can still bring a ban and a fine.

Review the Equine Prohibited Substances List on the FEI website and your own discipline’s rules. Some brands advertise testing or compliance accreditation, so ask the supplier for proof rather than relying on a label claim.

What Comfrey Cannot Replace

Comfrey is not a painkiller and does not replace a diagnosis. Lameness, colic and suspected ulcers all need your vet. Owners sometimes reach for herbs when the real answer is a prescribed medicine, such as omeprazole dosage for horses in confirmed ulcer cases.

Other Supplements Owners Compare With Comfrey

If you want gentler gut or calming support, a few other options have their own dosing guides. Our guide to hops dosage for horses covers calming and gut support. Psyllium husk dosage for horses explains fiber based gut care.

For recovery and gut lining, see glutamine dosage for horses. For trace mineral support, read our kelp dosage for horses guide.

Common Comfrey Mistakes

• Feeding fresh garden leaves by the handful
• Buying a root containing blend without checking the label
• Guessing the scoop size instead of weighing it
• Running comfrey for months with no break or vet review
• Using it alongside long term NSAIDs without telling the vet
• Dosing a pony or mini by “scaling down” the horse amount

Key Takeaways

• Label amounts are about 20 to 30 g of dried leaf or 10 to 20 ml of 1:3 tincture per day, split across two feeds.
• No verified weight based dose exists, so do not scale for ponies or minis.
• Comfrey contains liver toxic PAs that build up over time, and drying does not remove them.
• Keep courses short, around one month, and ask your vet about breaks and liver tests.
• Avoid it in pregnant mares, liver compromised horses and horses on long term NSAIDs.
• Competition riders should check prohibited substance rules and supplier testing.

Frequently Asked Questions

Conclusion and Next Steps

Comfrey dosage for horses comes down to three habits: measure it, keep it short and involve your vet. Weigh your dried leaf or syringe your tincture, use the label range, and stop after about a month. Before you begin, ask your vet whether a baseline liver check makes sense.

If your horse is dealing with pain or a slow healing injury, get a proper diagnosis first, then add comfrey only if your vet agrees.

Sources and Further Reading

• IVIS Guide to Poisonous Plants: Symphytum officinale
• UK Committee on Toxicity: Statement on Pyrrolizidine Alkaloids in Food
• University of Kentucky Equine Programs: Common Equine Hepatotoxins
• Feedipedia: Russian Comfrey
• Hilton Herbs: Comfrey Leaf
• FEI: Equine Prohibited Substances List