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Olidus

mg/dl vs mmol/l

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I am new to Diabetes and new to this forum.

Still learning all the lingo and what not.

 

I have noticed that alot of you talk mg/dl when it comes to readings? Since I have been diagnosed I have been taught to take my readings in mmol/l and pass that information along.

 

Is this another US thing? And Canadians use mmol/l?

Can anyone offer some insight as to what is the standard?

I know it all comes down to oranges and apples but want to make sure I am on the page as everyone else.

 

Thanks in advance

 

Mark K~

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And just an FYI....to get from one to the other just multiply/divide by 18. It's technically not an exact 18, but that number works for the most part unless you convert like 30 mmol to mg/dl then you may be off 1 mg/dl which is minor.

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no it's just a UK thing - like us driving on the left, when everybody else drives on the right (the notable exceptions have been evilly influenced by us Brits)

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I use the multiply by 18 to convert. As Jedi said, it is not exact, but it gives you a good idea.

 

I just use the computer calculator.

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Its mg/dl versus mmol/dl (diciliter not liter of blood).

 

I believe mmol/dl is the proper scientific way to read bgl, but I use mg/dl since I was raised in the US.

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Hi all, Stop knocking the Brits "mmol/l is millimoles/liter, and is the world standard unit for measuring

glucose in blood. Specifically, it is the designated SI (Systeme

International) unit. "World standard", of course, means that mmol/L is used

everywhere in the world except in the US." Quote taken from "What are mg/dl and mmol/l? How to convert? Glucose? Cholestrerol"

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WARNING: Science and math content!

 

I saw some mentions of "multiplying 18 (or dividing by 18)" as not being precise, but I respectfully disagree, unless you're interested in getting to hundredths or even thousandths of a gram in precision, which is useless information in terms of measuring blood glucose!

 

And since I like stoichiometry so much, here's a lesson to prove that multiplying and dividing by 18 is indeed very, very precise!

 

Millimoles per liter (mmol/L) is the way the world (including most of the scientific community) shares blood glucose concentrations. This is a count of the actual physical count of glucose molecules (moles) per liter of blood.

 

The USA decided that counting glucose molecules was too complicated, and hence, uses milligrams per deciliter (mg/dL), which is the weight of the glucose per deciliter.

 

To convert from the number of glucose molecules to the weight, we must know much one mole of glucose molecules weighs. Glucose is made up of C6H12O6. Carbon's mass is ~12 grams per mole, hydrogen's mass is ~1 gram per mole, and oxygen is ~16 grams per mole.

 

Thus, one mole of glucose weighs [(6*12)+(12*1)+(6*16)], or ~180 grams per mole.

 

Please note that very minute differences between atomic masses would cause this to be somewhere in the range of of a few nanograms of 180 grams per mole (depending on the proton count of each individual atom, but they all measure out to be the approximate masses as listed above--let's not go there, I don't think anyone is counting that closely!). We can safely say with one significant figure that it is 180.0 grams per mole. Good 'nuff. (If you really want to challenge it, look on the periodic table for the average atomic masses.)

 

That's how we convert 1 mole of glucose into 180 grams of glucose. They're equivalent. If I hand you 180 grams of glucose, I'm handing you one mole of glucose (approximately 6.022x10E23 molecules of C6H12O6).

 

Still with me? Good.

 

Since the world uses mmol/L as a measurement, let's start out with one mole of glucose dissolved in 1 liter of solution (we can assume it's blood, but it could be water, too). We know this is the same thing as 180 grams of glucose dissolved in 1 liter of solution.

[font="Fixedsys"]
1 mole     180 grams
------ = ------------
1 liter     1 liter
[/font]

 

We are interested in millimoles (not moles) and milligrams (not grams), so multiple each side by 1000, and we'll see the old units cancel out.

 

[font="Fixedsys"]
1 mole   1000 millimoles       180 grams    1000 milligrams
------ * ---------------  =  ------------ * --------------
1 liter       1 mole            1 liter         1 gram
[/font]

 

This leaves us with the following (mmol = millimoles, and mg = milligrams):

[font="Fixedsys"]
1000 mmol     180,000 mg
---------- = ------------
1 liter       1 liter
[/font]

 

 

Now let's see how many milligrams is in one mmol. Divide by 1,000 on each side so we can see what 1 mmol is in milligrams:

 

[font="Fixedsys"]
1 mmol     180 mg
------- = --------
1 liter    1 liter
[/font]

 

Not done yet! We also know that there are 10 deciliters in 1 liter of solution.

 

[font="Fixedsys"]
1 mmol     180 mg      180 mg       1 liter          18 mg
------- = -------- = -------- *  -------------- = ------------
1 liter    1 liter    1 liter    10 deciliters    1 deciliter
[/font]

 

Now, we can finally see how 1 mmol/1 L = 180 mg / 1 dL.

 

[font="Fixedsys"]
1 mmol       18 mg
------- = -----------
1 liter    1 deciliter
[/font]

 

 

QED. 1 mmol/L = 18 mg/dL

 

For what it's worth, we could find what 1 mg/dL equals in millimoles, but we'd start dealing with some real numbers.

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I saw some mentions of "multiplying 18 (or dividing by 18)" as not being precise, but I respectfully disagree, unless you're interested in getting to hundredths or even thousandths of a gram in precision, which is useless information in terms of measuring blood glucose!

 

And since I like stoichiometry so much, here's a lesson to prove that multiplying and dividing by 18 is indeed very, very precise!

 

Technically, it would be 18.016. Like I said though, unless you get really high (as in 700+ mg/dl), it's pointless and even then only 1 mg/dl off.

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Let's wait until we get a glucometer that has that kind of precision and we'll start including more than one significant figure!

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Let's wait until we get a glucometer that has that kind of precision and we'll start including more than one significant figure!

 

In the meantime, get out more often math freak. LOL :T

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WARNING: Science and math content!

Oh my gosh! Doesn't that qualify as cruel and unusual punishment now? ;)

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When you begin with a number which has an accuracy of + or - 20% what difference does it make whether one multiplies or divides by 18 or 18.016? Moot point right?

JayP

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But what if you're comparing whole blood calibrated meter values (like most in the UK) to plasma calibrated? Then you'll also have to multiply by 1.12...

 

*ducks*

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Can't see how it makes much difference when the testers ar 20% off all the time. 20% is disgraceful and its about time these moneygrabbing metre makers did something about it.

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