Calculating a dose of ivermectin for scabies

The short answer

Take your weight in pounds, divide by 33 and that’s how many 3 mg ivermectin pills you get.

Or divide by 67 and that’s how many 6 mg ivermectin pills you take.

To measure using kilograms, take your weight in kg. and divide by  15 and that’s how many 3 mg ivermectin pils you get. Or divide by 30 and that’s how many 6 mg pills you take.

With ivermectin horse paste turn the ring on the plunger to the weight and squirt that amount out as a dose. See the video about how to do this on this page.

Such a dose can be taken once or twice a week.

The long answer

I understand why people might be nervous about figuring and measuring their dose of a medicine, but ivermectin is very forgiving. Why? Partly because millions of people have taken billions of doses, often in places where there are no doctors, and there are almost no bad side effects. 

Also, if you take ivermectin with a meal you can absorb 2.5 times as much ivermectin than if you took it on an empty stomach! So even if you are hype-picky about figuring and measuring your dose there is a huge range of how much your body will actually absorb!

So when I took my eight 3mg ivermectin pills the dose might look like a 24 mg but my body might make use of anywhere from 10 mg to 24 mg!

After testing Merck (the maker of ivermectin…they call it Stromectol) arrived at the dose of 200 mcg/kg (mcg means micrograms or a millionths of a gram)) but it isn’t all that exact. 

Merck’s data sheet (pg 4) does specifically say “STROMECTOL should be taken on an empty stomach with water.” but if you do you will be absorbing the minimum amount. If you took it after a meal that might be like taking 500 mcg/kg (2.5 times as much).

So I encourage you to relax about measuring out a single dose, but not to take it more than twice a week.

Why? Because it takes about 3 days for ivermectin to work it’s way through your body. If you take it too often it will build up to too high a dose. Look at the chart down below; you can see how ivermectin levels drop over time.

Here’s an example. Suppose you took 10 mg  on Monday. By Tuesday at there would still be 42% of it in you or 4.2 mg. So let’s say on Tuesday you took another 10 mg.  That 10 mg is on top of the 4.2 mg already in you so you now have  14.2 mgs of ivermectin floating around in you. That’s still pretty close to a usual dose.

But what if you took another 10 mg dose on Wednesday? You still have 42% of that 14.2 mg in you which equals around 6 mg.  So now you have 16 mg of ivermectin floating around in you. Hopefully you can see you are headed towards a new high each day. Eventually you start to get symptoms of an overdose (tunnel vision, dizziness, etc).

The good news is if you do overdose the symptoms are reversible. All you have to do is wait and your body will process out the extra. In 18 hours half of it will be gone. After 3 days (72 hours) your body will be down to around 7% of whatever was in you.

Even the CDC says “Depending on [scabies] infection severity, ivermectin should be taken in three doses (approximately days 1, 2, and 8), five doses (approximately days 1, 2, 8, 9, and 15), or seven doses (approximately days 1, 2, 8, 9, 15, 22, and 29).” Notice how they are recommending taking it two days in a row (the first 2  weeks)? In that case you would have a much higher level of ivermectin in your system on the second day.

How to figure a dose of ivermectin for scabies

To figure a dose you just multiply 0.09 times the weight of the person in POUNDS.

Or you can multiply 0.2 times the person’s weight in KILOGRAMS.

That’s how many mg (milligrams) your dose is.

For instance, if you weigh 150 lbs, you multiple 150 x .09 = 13.5 mg. 

That means you’d need 4.5 three mg pills…rounded off to 5 three milligram pills.

Where did I get those numbers?

The usual dose for humans is 0.2 mg/kg (milligrams pr kilogram) (note: .2 mg = 200 mcg)

That equals 0.09 mg/lb (milligrams per pound) (note: .09 mg = 90 mcg)

1 kg = 2.2 lbs

0.2 mg divided by 2.2 = 0.09 mg/lb (milligram per pound)

Ivermectin pills come in two doses: 3 mg and 6 mg

3 mg divided by 0.09 mg/lb = 33.3 pounds per 3 mg pill

6 mg divided by 0.09 mg/lb = 66.7 pounds per 6 mg pill

So depending on which pills you got you just divide your weight in pounds by either 33 or 66 and that’s how many pills you take as a dose. But, of course, your doctor will do that for you.

Ivermectin Horse Paste comes in syringes which contain 6.08 grams total weight.

The paste in the syringe is 1.87% ivermectin.

6.08 grams x .0187% = 0.11 grams of ivermectin

0.11 grams = 110 mg (milligrams)

110 mg divided by 0.09 mg/lb = 1,222 pounds

So one syringe of horse paste is enough to treat 1,222 pounds!

That’s why the ivermectin horse paste packages say “Contents will treat up to 1250 lb body weight”.

So I could use the ring on the syringe’s plunger to measure my dose exactly as is done for a horse!

Disclaimer: Ivermectin horse paste specifically says “For Oral Use in Horses Only”.  I am NOT advising you to take horse paste! I am just sharing what I did and my experiences. You have to decide what to do or not for yourself.

Measuring a small dose

The syringe isn’t all that accurate…it has a bit of slop. So I tended to err a bit on the high side.

But one nice trick is to set the ring for double the dose and squirt that onto a plate. Then divide that in half using a razor blade or a business card. I’d scoop up that half and take that as my dose. I’d toss out the other half.

Another trick is to squirt out a double dose, then add a couple tablespoons of applesauce and stir it up. Then I could measure out a tablespoon and use that as my dose.

These tricks are especially handy when measuring for smaller people. It’s a lot easier to measure a big dose for 200 pounds than a tiny dose for 100 pounds!