This page is not veterinary advice. Paw Multiverse is not a veterinary practice. We cannot examine, diagnose or treat your animal. There are no medicines here, no doses, no home remedies and no treatment steps, on purpose. If your pet is unwell, has swallowed something, or has changed in a way you cannot explain, ring your vet or your nearest emergency clinic and let them decide. Full disclaimer.
Onion poisoning is the one that catches careful owners out, because almost nobody feeds a dog an onion. They feed it gravy, or the last of the casserole, or a bit of stuffing, and then five days later the dog is flat and nobody connects the two events.
That five-day gap is the single most important thing on this page. Everything else here is detail around it.
Allium exposure, against the figures MSD publishes
This reports what one veterinary reference publishes for raw onion. It is not an assessment of your animal, and it will never tell you your pet is fine. Every result ends at a phone call.
If what was eaten was garlic, leek, chive, shallot or a cooked or powdered form, read the section below on why we cannot convert it for you.
Figures read on 4 August 2026 from the MSD Veterinary Manual entry on garlic and onion (Allium spp) toxicosis in animals, and from Pet Poison Helpline. Both are named in the result.
What the sources say is actually happening
The MSD Veterinary Manual, read on 4 August 2026, attributes the damage to “Sulfur-containing oxidants in Allium spp”. Those compounds attack red blood cells directly. The entry describes “oxidative damage to RBCs, Heinz body formation, and methemoglobinemia, which begins within 24 hours and peaks in approximately 72 hours”, with haemolysis typically following “3-5 days after exposure”.
Two separate things are happening in that sentence and it is worth separating them. Methaemoglobinaemia is haemoglobin that has been chemically altered so it can no longer carry oxygen properly. Haemolysis is red blood cells breaking apart. The first can start within a day. The second usually arrives towards the end of the week. An animal can therefore be measurably affected long before it looks affected, and can then deteriorate sharply at a point when the meal has been forgotten.
MSD lists the signs as “Lethargy, anorexia, tachypnea, tachycardia, weakness, exercise intolerance, icterus, hemoglobinuria, collapse, and death may occur”. Read that list and notice how unspecific the early items are. Tired, off food, breathing a bit fast. That describes a hundred things, which is exactly why the history matters more than the symptom.
Why cooking, drying and powdering do not help
This is the most common misunderstanding about Allium species and it is settled in the sources. MSD states that toxicosis has been reported after ingestion of “raw, cooked, dehydrated, or granulated” onions and garlic. Heat does not destroy the responsible compounds.
Dehydrated forms are arguably the greater practical risk, because they are concentrated and because they hide. Onion powder and garlic powder appear in stock cubes, gravy granules, crisps, sausages, baby food, pasta sauces and a great many things marketed as savoury. A dog that has never been given an onion can still have had a considerable amount of onion.
The MSD figure for cats makes the point sharply, because it is expressed two ways in the same sentence: “less than a teaspoon of cooked onions or 5 g/kg of raw onions”. A teaspoon. That is the sort of quantity that ends up on a plate by accident.
The figures, and their limits
| Species | What MSD publishes | What it does not say |
|---|---|---|
| Dog | “ingestion of 15-30 g/kg of raw onion has resulted in clinical signs” | It does not name a level below which nothing happens, and it does not address repeated small exposures, which is the pattern most dogs actually have. |
| Cat | “toxicosis has been reported in cats after ingesting less than a teaspoon of cooked onions or 5 g/kg of raw onions” | It does not convert cooked to raw, and it does not give a figure for garlic, leek, chive or shallot. |
| Both | “Cats are the most susceptible species, followed by dogs.” | It does not quantify the difference beyond the two figures above. |
Pet Poison Helpline, read the same day, takes the opposite editorial position and publishes no figure for garlic at all. Its stated reason is that “a number of factors (amount of substance ingested, size of the animal, allergies, etc.) determine what is toxic to a particular pet”. It does add a genetic dimension the MSD entry does not: it names cats and Japanese breeds of dogs, “e.g., Akita, Shiba Inu”, as particularly vulnerable.
We looked for a published conversion factor between garlic and onion by weight, since garlic is widely described as the more potent of the two. We could not find one in either source. The tool above therefore asks only about raw onion, and if what was eaten was garlic we would rather tell you we cannot convert it than hand you a number we made up.
day 0 onion, garlic, leek or chive eaten
| (raw, cooked, dried or powdered:
| the source says all of them)
|
day 1 oxidative damage to red cells,
| Heinz bodies, methaemoglobin
| begin (MSD: within 24 h)
|
day 3 that process peaks
| (MSD: approx. 72 h)
|
day 3-5 haemolysis typically occurs
v (MSD)
the animal may look completely well
through days 0 to 2. that is the trap.
the phone call belongs on day 0.
Garlic supplements, and the flea-repellent claim
Garlic is sold for dogs. It appears in supplements, in some treats, and in a long-standing folk belief that it repels fleas. We are not going to review any product, because this site does not do brands, but the underlying question deserves a straight answer.
Pet Poison Helpline states without qualification that garlic “along with chives, onion, and leeks, belongs to the Allium family; all are poisonous to dogs, cats, and livestock”. MSD groups garlic with onion throughout its entry and reports toxicosis from dehydrated and granulated forms. Neither source we read distinguishes a supplemental dose from a dietary one, and neither publishes an amount described as acceptable.
We could not find any source of that standard supporting the flea claim. That does not prove it false. It means that if you are giving garlic to a dog for that reason, the person to discuss it with is your vet, who can weigh it against your dog rather than against an average.
What we could not source
We could not find a published safe quantity of any Allium for either species. The figures above are levels at which harm has been reported, not levels below which it has been excluded.
We could not find a garlic-to-onion potency ratio, a cooked-to-raw conversion, or any figure at all for leek, chive, shallot or spring onion.
We could not find, in the sources we read, an explanation for why cats are the most susceptible species. MSD states it as a fact without giving the biological basis. Pet Poison Helpline names the Japanese breeds without explaining the mechanism either.
We could not source any at-home step. There is nothing here about making an animal sick, because decontamination is a clinical decision and the sources that discuss it are written for clinicians.
Printable: what to tell the vet
Ticks are held until you reload. Print it for the kitchen drawer.
The exposure
The animal
The clock
Related pages
For the longer read on each food, see onions and dogs, garlic and dogs, onions and cats and garlic and cats. The poison control directory puts every kitchen risk on one printable sheet with its sources. Other published thresholds live on the grape and raisin checker, the xylitol checker, the chocolate calculator and the human painkiller checker. If it has already happened, go to my dog ate something or my cat ate something, and before you call the vet will help you describe it.
Why this checker stopped giving verdicts
The previous version of this tool sorted your answer into an urgency band and told you which one you were in. That has gone, deliberately, and it is worth explaining rather than quietly changing.
A band is a claim about your animal. This page has no information about your animal. It has a weight you typed and an amount you estimated, probably from a pan you had already half emptied. The MSD figures are levels at which harm has been reported in some animals, not boundaries with anything meaningful on the safe side of them, and one of our two sources declines to publish a figure at all. Turning that into a colour-coded answer would be inventing certainty at the exact moment somebody is most inclined to believe it.
There is a second reason, specific to Allium. Because haemolysis arrives three to five days later, a reassuring result today would be reassuring at precisely the point when the animal cannot yet look ill. A tool that says “low risk” on day zero is not just imprecise. It is imprecise in the direction that costs the most.
So the tool now reports, attributes and dates. Then it sends you to a vet, in every branch, including the branch where your figure is small. If your figure is small, say so on the phone; that is genuinely useful information for the person triaging the call. It is just not a decision you or this page should be making.
The repeat-exposure problem nobody puts on a chart
Almost every published figure for onion is a single-event figure. Somebody ate a bowl of something once, and that is the case that got written up. The exposure pattern in ordinary households is different and no source we read addresses it directly.
The mechanism gives a reason to take it seriously anyway. Oxidative damage to red cells is cumulative in the sense that the body has to replace what was destroyed, and a supply of fresh oxidant arriving every Sunday does not give it a clear run. MSD does not quantify this, and we are not going to. What we can say is that the question “has this happened before?” is one your vet will ask, and it is worth having an honest answer ready rather than a hopeful one.
