Dose: How much is too much for Your Animal?

dose of dog

Today I learned I was 4,550,000 milligrams of dog.  Is that fat?

Toxicity is determined by dose….

For the vast majority of poisons, the signs we see are controlled by how much of the poison a pet has ingested. This will be different for everything (the amount of ibuprofen it takes to make a dog’s kidneys fail is larger than the amount of naproxen it takes, for instance). I hope to help you understand why this is not easily done at home, and why your vet requires a specialist to treat a case of poisoning.

Anything can be toxic.  Anything.  Even waterGiven the proper amount of an ingested substance, anything on the planet can make you ill, or kill you. A good veterinary professional will be able to provide you with the answer to several pieces of information about whatever your pet has ingested:

  • Your pet’s dose by body weight – expressed in milligrams per kilogram (We’ll dive into how that is determined below)
  • The therapeutic dosage (if applicable) – if your pet swallowed a medication, the therapeutic dose is how much we normally would give a dog of comparable size.
  • A threshold dose – this can be called many different things, but this is the lowest dose for a specific substance that will cause signs of illness.
  • LD50 – this is a fancy term in toxicology that you frequently see.  It just indicates the specific dose at which 50% of the test population died after taking a substance. This is often considered to be the lethal dose.
  • The margin of safety – this  is typically determined by the difference between the therapeutic dose and the threshold dose. Drugs with a wide margin of safety are safer than drugs with a narrow margin of safety.
  • The serum or plasma half-life – this is the amount of time it takes the body to get rid of half of the amount of an ingested substance.

…But there are other things involved

While this all sounds pretty straightforward (if a bit complicated), there are several factors that will influence a poison’s effect on the body:

  • Other medications a pet is taking – Some medications will enhance or hinder each other. A medication that would normally be safe might be lethal in combination with another medication.
  • The pet’s health history – certain diseases will affect how a pet metabolizes a medication, making it more difficult for them to clear it out of their body.
  • Formulation – some medication come in both instant release and extended release form. Extended release medications take longer to take effect, and will last longer in the body.

All of this information is necessary for a veterinarian to be able to determine how something will affect your pet!  This is often why a practicing vet will not know the specifics on how a case of poisoning must be treated.  Toxicology is a specialized field, and veterinarians will often refer an owner to a poison control center to assess all of this information, (the above is what you pay for when you call an animal poison control center, not just the recommendation of whether to take your pet into the vet).

There are other important things a poison control center or toxicologist will be able to tell you or your vet:

  • If it is safe to induce vomiting – if something is expected to cause signs quickly, we may not want to do this.
  • What signs we can see at the specific dose your pet ingested
  • What medication can reverse or control those specific signs
  • How long before a poison takes effect
  • How long the effects will last
  • Whatever long-term effects may apply


So, how do I tell how much my pet has ingested?

how much is the dose?

I might as well be written in alien

Calculating a dose can be very complicated.  Information on toxicity is presented in a milligram per kilogram format (mg/kg), and the key to seeing if something is toxic lays in determining how many milligrams of a specific poison is any a food, medication, plant, or other substance.

If the lethal dose of a medication is 25 mg/kg, this does NOT mean that giving 25 milligrams to your pet will kill it!!

In terms of determining how much of something will be poisonous, we always go my how much a pet got by body weight. For a simple example, let’s see how much sugar a pet gets from a pill:

A 10 pound dog swallows a 25 milligram sugar pill:

  • 10 pounds is equal to 4.55 kilograms
  • 25 milligrams divided by 4.55 kilograms equals 5.49 milligrams per kilogram (5.49 mg/kg) of sugar per dog

A 65 pound dog swallows the same 25 milligram sugar pill:

  • 65 pounds is equal to 29.55 kilograms
  • 25 milligrams divided by 29.55 kilograms equals 0.85 milligrams per kilogram (0.85 mg/kg) of sugar per dog

Sounds easy, right?  Let’s make it a bit more complicated:

A 10 pound dog swallows 10 ounces of chocolate that contains 25 milligrams of sugar per ounce (this is not an accurate example of how much sugar is in chocolate, just used as an example):

  • 10 pounds still equals 4.55 kilograms
  • 10 ounces of chocolate times 25 milligrams of sugar per ounce equals 250 milligrams of sugar
  • 250 milligrams divided by 4.55 kilograms equals 54.95 milligrams per kilogram (54.95 mg/kg) of sugar per dog

Keep in mind that in the above, we calculated how much sugar the pet ingested, NOT how much chocolate, nor determined how much chocolate was lethal.

If I haven’t lost you yet, let’s do one final bit of work to make you especially confused:

A 10 pound dog swallows 15 cookies, each containing 10 ounces of chocolate with 25 milligrams of sugar per ounce (let’s see if I’ve managed to confuse even myself!):

  • 10 pounds of dog will always equal 4.55 kilograms of dog (to amuse veterinary professionals, this is 4,550,000 milligrams of dog)
  • 15 cookies times 10 ounces of chocolate per cookie equals 150 ounces of chocolate in total
  • 150 ounces of chocolate times 25 milligrams of sugar per ounce equals 3,750 milligrams of sugar per 10 ounces or per 15 cookies
  • 3,750 milligrams of sugar divided by 4.55 kilograms of dog equals 824.18 milligrams per kilogram of sugar per dog (824.18 mg/kg)

We could continue to complicate things, but it gets highly confusing when we’re dealing in substances that have milligrams per milliliter, percentage of concentration, or parts per million (ppm).

Please don’t try to do this all yourself at home if your pet swallows something.  Even in the veterinary field, we want other people checking our math to make sure our numbers are free of error.  Your pet’s life could be at stake.  Call someone who does this daily, and can do it quickly.


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