Pg/ml vs Ng/L ? whats the difference ?

[ozwald28]

Hey guys

Sorry if this is a really silly question.

Im seeing a lot of different numbers popping up for b12 levels and i am confused by the interchange of the use of pg/ml vs ng/l ? i just wonder what the difference is ?

[Parlay]

Not a silly question at all. Just a measurement of fluid. Picograms per millimetre versus nanograms per litre.

[Nackapan in reply to Parlay]

Writing at the same time!

[Nackapan]

Not silly Pg = picogram

Ng = nanogram

No idea why different labs use different measures

1 pg a larger units than a ng

Just look at the reference ranges

I'm sure a scientist csn explain more 🤔

[helvella]

Nothing.

When dealing with fractions (and anything that is a unit per unit is a fraction), if you multiply both top and bottom numbers by the same number, it makes no difference. Or if you divide.

1/2 = 10/20 = 100/200 = 1000/2000

And a nanogram is a thousand times a picogram, a litre is a thousand times a millilitre.

And that is all that has happened. Someone had to decide what units to use and the coin spun one way for one lab and the other way at another lab.

But be careful, if the units are pmol, there is a difference. Effectively ng or pg refers to the mass (or weight) of B12 present. Whereas pmol refers to the number of molecules of B12. Numerically they are not very different for B12 - but different enough to be important.

You can play about with units here:

unitslab.com/node/141

[Gambit62 Administrator]

whilst there isn't any difference between Pg/ml and Ng/L there is another common measure which refers to moles (the number of molecules) in a particular volume - can't remember what the usual units are but will be something lime having and m rather than a g before the slash. Because B12 is a very large molecule there isn't much difference in the units but when it is used for other vitamins - eg folate - which is much smaller the difference can be quite significant (and the ranges will also be very different).

[ozwald28]

Thanks so much everyone - thats satisfied my curiosity indeed!