My dog ate chocolate but seems completely fine. Is he out of danger?

Not necessarily. Chocolate signs typically start 6 to 12 hours after eating, so a normal-looking dog an hour later tells you about the clock rather than the dose. What matters is the type of chocolate, how much, and your dog's weight — call with those three numbers rather than waiting for a symptom to settle the question.

How long after eating something toxic will a dog vomit?

If the substance irritates the stomach, usually within one to three hours. But many of the dangerous poisonings do not cause early vomiting at all — grapes, xylitol, antifreeze and vitamin D can all leave an animal looking well while the kidneys or liver are affected. No vomiting is not reassurance.

Should I make my dog vomit?

Only if a vet or a poison line tells you to. It is actively harmful after anything corrosive or petroleum-based, and dangerous in an animal that is already drowsy, seizing or struggling to breathe. Hydrogen peroxide, the usual home method, can injure the stomach lining on its own.

What if I do not know how much they ate?

Say so, and give the worst case you cannot rule out — the whole bar, the rest of the packet. Vets plan treatment around the maximum plausible dose. Guessing low to sound less alarming is the one thing that genuinely costs time.

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How Long Until Symptoms Show

Published September 17, 2026 · PawLife editorial team

Poisoning rarely announces itself. A dog eats something off the counter, acts completely normal for the rest of the evening, and the owner decides it cannot have been serious. For a few substances that reasoning is correct. For several of the most dangerous ones it is exactly backwards: the quiet hours are when the damage is being done, and the symptoms arrive once it is harder to undo.

This page is about that gap. It lists how long it typically takes for signs to appear after 27 common poisonings, explains why some take days, and sets out what a vet will ask you for when you call. It is not a substitute for that call.

If it has just happened, call first and read afterwards.

Your own vet, an emergency clinic, or a poison line: ASPCA Animal Poison Control in the US, or Animal PoisonLine (01202 509000) in the UK. Neither of them will tell you to wait and see how it goes, which is the advice you will otherwise give yourself.

How long until signs appear

These are typical ranges from the veterinary literature, and every one of them has exceptions in both directions. Read them as an explanation of why the vet wants to know when it happened, not as a schedule you can plan around. Each substance links to its own page, which carries the mechanism, the dose thresholds and the sources.

Substance	What does the damage	When signs appear
Xylitol	Xylitol, a sugar alcohol	10 to 30 minutes for hypoglycaemia. Liver injury may not show for a day or more.
Alcohol	Ethanol	15 to 30 minutes
Coffee & Caffeine	Caffeine, a methylxanthine	30 minutes to 2 hours
Cannabis Edibles	THC, usually alongside chocolate, xylitol or butter	30 minutes to 3 hours by mouth
Oleander	Oleandrin and other cardiac glycosides	30 minutes to a few hours
Sago Palm	Cycasin	15 minutes to 6 hours for vomiting; liver failure at 2–3 days
Slug Bait	Metaldehyde	30 minutes to 3 hours
Salt	Sodium chloride	1 to 3 hours
Mothballs	Naphthalene or paradichlorobenzene — and which one matters	Within a few hours
Raw Yeast Dough	Live yeast — producing ethanol and carbon dioxide	Distension within 1–2 hours; intoxication builds over 2–6 hours and keeps going
Acetaminophen (Paracetamol)	Acetaminophen / paracetamol	Cats: 1–4 hours. Dogs: liver signs at 24–72 hours.
Essential Oils	Phenols and terpenes — tea tree, pine, citrus, wintergreen, eucalyptus	Within 2 to 8 hours for skin or oral exposure
Ibuprofen	Ibuprofen, a non-selective NSAID	2 to 6 hours for gastrointestinal signs; kidney values move over 12–48 hours
Macadamia Nuts	Unidentified	3 to 12 hours
Antifreeze	Ethylene glycol	30 minutes to 12 hours, in three distinct phases
Lilies	Unidentified nephrotoxin in Lilium and Hemerocallis species	Vomiting within 1–3 hours; kidney values rise by 18–72 hours
Autumn Crocus	Colchicine	2 to 12 hours for gastrointestinal signs; marrow effects at 3–7 days
Iron Supplements	Elemental iron	Within 6 hours, often with a deceptive lull afterwards
Chocolate	Theobromine and caffeine (methylxanthines)	6 to 12 hours, occasionally sooner with cocoa powder or espresso-based products
Grapes & Raisins	Suspected tartaric acid and potassium bitartrate	Vomiting within 6–12 hours; kidney values rise over 24–72 hours
Onions	N-propyl disulfide and related organosulfur compounds	Vomiting within hours; anaemia at 1–5 days
Garlic	Organosulfur compounds, about five times more concentrated than in onion	Vomiting within hours; anaemia at 1–5 days
Naproxen	Naproxen, a long-acting NSAID	Hours, but signs can appear days later because of the persistence
Wild Mushrooms	Depends entirely on species — amatoxins, muscarine, ibotenic acid, hydrazines	Under 6 hours usually means a less dangerous species. Over 6 hours raises the possibility of amatoxins.
Vitamin D Supplements	Cholecalciferol (vitamin D3)	12 to 36 hours
Rat Poison	Four different active ingredients with nothing in common	2 hours to 5 days depending entirely on which one
Cooked Bones	None — this is mechanical injury, not poisoning	Immediate for choking; hours to days for obstruction or perforation

Why some poisons wait

The delay is not random. It follows what the substance actually does.

Things that irritate the gut act fastest, because the gut reacts to contact. Vomiting within an hour or two is the usual pattern, and it is also the least informative sign — plenty of harmless meals do the same.
Things that interfere with metabolism follow the bloodstream. Xylitol drops blood sugar within half an hour because it triggers an insulin release; the liver injury it can also cause may take a day or more to show up. One substance, two clocks.
Things that damage an organ are the slow ones, and the dangerous ones. Grapes, lilies in cats, antifreeze, vitamin D and the human painkillers all injure kidneys or liver before anything looks wrong from the outside. By the time the animal seems ill, the blood work has usually been abnormal for a while.

The ones where waiting is the mistake

If any of these is on the table, the absence of symptoms is not information. Call now, not in the morning.

Xylitol (sweetener in gum, peanut butter, some medicines) — minutes to hypoglycaemia, and a normal-looking dog can still be heading for liver failure.
Grapes, raisins and sultanas — no established safe dose, and kidney values move over the following days.
Lilies, for cats — pollen on the fur is enough, and the kidneys are usually the first thing affected.
Antifreeze — treatment has a window measured in hours and the middle phase looks like recovery.
Paracetamol and ibuprofen — cats have almost no tolerance for paracetamol; in dogs the liver signs can be two or three days behind the swallowing.
Vitamin D supplements and rat poison — both are slow, both are serious, and rat poison depends entirely on which chemistry is in the box. Keep the packaging.

The three numbers the vet will ask for

Every poisoning call starts the same way, because the answer depends on arithmetic more than on how ill the animal looks.

Weight. Toxicity is measured per kilogram. The same square of baking chocolate is a different problem for a 4 kg terrier and a 40 kg labrador, and "about medium sized" is not a number anyone can use.
How much, and what exactly. Brand, percentage, the packet if you still have it. Seventy per cent dark and a milk chocolate bar are not the same substance for this purpose.
When. The clock starts at the swallow, not at the symptom. Thirty minutes ago and six hours ago lead to completely different treatment.

Two of those three are easier to answer if they were written down before the emergency. PawLife keeps a weight history with the dates, and the food safety lookup is in the app and free to read on this site without installing anything.

What not to do while you wait for the callback

Do not induce vomiting unless a vet has told you to. It is the wrong move for anything corrosive, for petroleum products, and for an animal that is already drowsy or seizing, and hydrogen peroxide has its own risks.
Do not give milk, salt or anything else from a forum. Salt in particular is a poison in its own right, and it has an entry in the table above.
Do not wait for a symptom to confirm your suspicion. The substances that reward waiting are the ones that were never going to hurt anyone.
Do keep the packaging. For rat poison and medicines it changes the treatment.

Sources

Onset ranges and mechanisms on this page come from the per-substance pages in our food safety database, which cite their own sources: principally the Merck Veterinary Manual and ASPCA Animal Poison Control. Those entries were last checked against the sources on August 18, 2026. When they are checked again, this date moves.