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Why do American and English meters use different units?

Steffany

Steffany

Member
Messages
13
Type of diabetes
Type 1
Treatment type
Pump
I've always wondered - why DO Americans and English meters use different units of measurements?
As someone who lives in the U.K. I find our system easier to understand; Americans are always dealing with such massive numbers. Maybe people are under the impression that us English need things dumbed down or something!
Also has any other English person had the heart attack moment your meter randomly decides to go into American units, and despite the fact that logically you know English home meters generally don't go above 33, you see that three digit number and freak your **** mind out?
 
Steffany said:
I've always wondered - why DO Americans and English meters use different units of measurements?
As someone who lives in the U.K. I find our system easier to understand; Americans are always dealing with such massive numbers. Maybe people are under the impression that us English need things dumbed down or something!
Also has any other English person had the heart attack moment your meter randomly decides to go into American units, and despite the fact that logically you know English home meters generally don't go above 33, you see that three digit number and freak your **** mind out?
Click to expand...

To be honest, I just view it a bit like why some countries measure distance in miles, and some in kilometres. Thankfully, my metre can only display to the UK standards, so I have been spared that angst at least!
 
Steffany said:
That converter is awesome! I can finally understand my American diabetic bretherin.
Click to expand...

You'll get the same result by dividing American mg/dl by 18 to get mmol/l. And multiplying mmol/l by 18 to get mg/dl.

I've no idea why different countries have adopted different methods.

The difference is that mg/dl measures weight of glucose in blood, and mmol/l measures the molecular concentration of glucose in blood.

Yeah, I know, I don't understand that either - I'm still trying to get my head round what a mole is: as far as I can see, it's not weight in terms of grams, which is what USA does. Instead, it's a measure of the number of glucose molecules kicking about in stream, which is a number, not a weight. Any scientists out there who can help me with this!?! Conceptually, I have a lot of difficulties with understanding what a mmol actually is!

Looking at it from a weight, mg/dl, point of view, it looks like 5 or 6 mmol/l works out at about 1g per litre of blood to keep us tidy. Realising that was useful for me. I've often been tempted to scoof food till hypo symptoms go away, but bearing in mind that your average Joe has about 10 to 12 litres of blood, 10 to 15g for your common or garden minor hypo makes a lot of sense.
 
I think this has to do with adoption of international units, ie the ISO system
The British have been fairly slow with this, keeping miles, pints etc, but most of industry (including medical) now use the ISO system. My industry (UK construction) went over to ISO decades ago. In the US, there is much more resistance, because they are largely self-sufficient.
 
BrianTheElder said:
I think this has to do with adoption of international units, ie the ISO system
The British have been fairly slow with this, keeping miles, pints etc, but most of industry (including medical) now use the ISO system. My industry (UK construction) went over to ISO decades ago. In the US, there is much more resistance, because they are largely self-sufficient.
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A lot of it is personal preference.

I always think of the distance between two towns that I'm travelling between in terms of miles, because that's what I'm used to.

Whereas, if I'm doing some DIY in the house, I prefer centimetres. Trivial answer is that B&Q uses that!

I'm not entirely sure why I pick and choose between the two systems. But I think it is important, as a tax paying citizen, that I'm able to do what is comfortable for me, without governments telling me which systems I should use.

Sorry, going off topic, so will say no more about it. Although, having just said that, to bring it back on topic again, I like my mmol/l and if anything is done to change that, there'll be barricades in front of the chemists....!
 
The UK systems make a lot more since to me then the USA system as I understand the concepts behind it from my A level chemistry (a very long time ago).

mmol/l allows chemical equations to be balanced easier then mg/dl, not that there is any reasons to wish to do so, other than passing exams.

A mole is a number of molecules. So for example 2 mole of H2 + 1 mole of O2 will give 2 mole of water (and lots of heat with a big bang).

The USA system tried to use units that a "normal person" can understand.

Both the UK and USA are using ISO units, just in a different way.
 
Canada, Australia, and most other developed countries use mmol/l just like the UK. There are a few holdouts just like there are a very few countries that have not adopted the metric system.
 
Scott-C said:
You'll get the same result by dividing American mg/dl by 18 to get mmol/l. And multiplying mmol/l by 18 to get mg/dl.

I've no idea why different countries have adopted different methods.

The difference is that mg/dl measures weight of glucose in blood, and mmol/l measures the molecular concentration of glucose in blood.

Yeah, I know, I don't understand that either - I'm still trying to get my head round what a mole is: as far as I can see, it's not weight in terms of grams, which is what USA does. Instead, it's a measure of the number of glucose molecules kicking about in stream, which is a number, not a weight. Any scientists out there who can help me with this!?! Conceptually, I have a lot of difficulties with understanding what a mmol actually is!

Looking at it from a weight, mg/dl, point of view, it looks like 5 or 6 mmol/l works out at about 1g per litre of blood to keep us tidy. Realising that was useful for me. I've often been tempted to scoof food till hypo symptoms go away, but bearing in mind that your average Joe has about 10 to 12 litres of blood, 10 to 15g for your common or garden minor hypo makes a lot of sense.
Click to expand...
A blood glucose measurement reported in mmol/l tells you how many molecules of glucose are present in each litre of blood. Just like dozen is a special word for 12, score is a special word for 20 and gross is a special word for 144, mole is a special word for 6.02214 × 10^23 (602,214 million million million)
1 mmol (= 1millimole) is the word for 1/1000 of a mole i.e. 6.02214 x 10^20

Why that particular number, you may ask? It's Avogadro's number/constant which is the number of atoms of carbon found in 12g of the carbon-12 isotope of carbon. https://en.wikipedia.org/wiki/Avogadro_constant

To convert mg/dl into mmol/l, first you have to multiply the value in mg/dl by 10 (as there are 10 decilitres in every litre). You then have to divide by the molecular mass of the substance being reported which depends on its formula. Glucose has the formula C6H12O6 so its molecular mass is (6x12) + (12x1) + (6x16) = 180. Multiplying by 10 and dividing 180 is the same as dividing by 18, hence a blood glucose of 180 mg/dl is the same as a blood glucose of 10 mmol/l.

Different substances have different molecular masses so the conversion factor of 18 only works for glucose. There is a list of more conversion factors here:- http://www.globalrph.com/conv_si.htm Reporting values in mmol/l makes it easy to see the relationships between the numbers of different types of molecules and is the SI (International System of Units) unit of choice for reporting laboratory values. It also allows easier communication between countries if everyone uses the same units.

The average blood volume is 5 litres (8 pints). https://en.wikipedia.org/wiki/Blood_volume
 
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