Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that your pup has eaten some caramelized onions.
Onions and garlic can be toxic
for dogs because they cannot digest them properly leading to nausea, vomiting, abdominal pain and cramping, red blood cell damage, anemia and secondary organ damage.
The toxicity is dose dependent however. That means that a dog must eat a certain amount of onions per pound of body weight to see signs of toxicity. They must eat 0.5% of their body weight of onions in order to see toxic effects. In a 9 pound dog that is 0.045 pounds (9lbs X 0.005 = 0.045) or 0.72 ounces (16 ounces X 0.045 = 0.72 ounces) of onions.
For reference a medium onion is about 6 ounces, so she would need to eat roughly 1/8th of medium sized onion.
Do you think that she ingested that amount of onions?
If so when is the last time that the onions were fed?
If it has been more than a couple hours it is too late for us to do much for her at home.
Activated charcoal will bind drug or chemical toxins, but it must be given within a period of time in order to work. If you want to give it a try she will need 1 GRAM per pound of body weight or 9 GRAMS (not milligrams).
But if she just ate the onions and you think she may have eaten a toxic amount it is best to induce vomiting.
Give her 1 tablespoon of 3% hydrogen peroxide soaked with some bread chunks or mixed with some ice cream
The take her outside and run her around.
If no vomiting in 15 minutes repeat the peroxide dose.
If she vomits the onions she should be fine.
If you don't have peroxide and are concerned that she ate a toxic amount then an emergency clinic visit to induce vomiting is best.
Once clinical signs develop, supportive care including intravenous fluids (to keep her hydrated) and oxygen therapy are the main forms of treatment. Some dogs may require a blood transfusion if their red blood cells are damaged enough.
The outlook for onion toxicity is good with early treatment but “guarded” in severe cases or in dogs that are not treated by a veterinarian.
Please let me know if you have any further questions.