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Good morning class and welcome to MLT lecture two. I hope you all were able to get 
hold of the first lecture? In the first lecture, we looked at what clinical chemistry is all 
about and the importance of clinical chemistry. In today’s Lecture we will be discussing S 
I Units and its application in clinical chemistry.

THE INTERNATIONAL SYSTEM OF UNITS (S I UNITS)

The SI units called systeme International d’ Units or International System of Units have 
now replaced the foot-pound- Second called Imperial system and the centimeter- gram-
second (cgs) system which were the old systems of reporting and measurement. The 
World Health Organization (WHO) recommended that the medical community 
throughout the world should adopt the International System of Units in reporting and 
measurement. So S I Units is now universally adopted.

S I units is accepted internationally. For this reason, it is understood in Nigeria 
France, Portugal, Germany, Japan, Greece, Italy or in Great Britain when is it used 
as a unit of measurement or to report the result of lab test .This allows useful 
health information to be exchanged within a country and between nations of the 
World. Any misunderstanding which can arise if each country or hospitals within 
a given country adopt its own units of measurement and reporting of laboratory 
test results can be ruled out. For this reason health institutions and laboratories 
must adopt the SI units.

-Writing laboratory test methods 
- preparing standard operating procedures 
-preparing of laboratory regents 
-Reporting of laboratory test result

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A base is the starting point or the foundation of something. S I base Units is therefore 
defined as the foundation where other units are formed or derived.

The international system of units is based on the metre-kilogram- second system. There 
are seven S I base units where all the other units are derived from as shown below:

SI BASE UNITS 
SYMBOLS 
QUANTITY 
MEASURED

SI DERIVED UNITS 
SI derived units are composed of SI base units 
SI DERIVED UNITS 
SYMBOL 
QUANTITY MEASURED

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A prefix is one or more letters which is added to the beginning of a word to 
modify its meaning. The S I Units prefixes enable the measurement of quantities 
larger or smaller than the base or the derived units to be measured. 
That is the use of a prefix makes a unit either larger or smaller. 
The S I units prefixes commonly used in laboratory measurements or reporting 
are:

The SI derived unit of volume is the cubic metre (M3). The litre has been used as  
the S I unit of volume. Litre is not an SI unit but it has been chosen as the unit of 
volume because the cubic metre M3 is a very large unit. Hence litre has been 
recommended for use in the laboratory as the unit of volume.

The S I Unit Of Volume Is Litre or L and 1  litre =1dm3

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Volume measurements are made in litres or multiples and submultiples of the 
litre such as dl =10-1litre, ml = 10-3 litre , µ l = 10-6 litre.

The kilogram (kg) is the SI unit for mass and gram (g) is the working unit therefore 
mass measurement are made in grams or in multiples and submultiples of the 
gram.

The SI unit of length is the metre (m). Measurements of length are made in 
metres or in millimeters.

The mole (mol) is the SI unit of the amount of substance. All measurements of the 
amount of substance are made in moles.

1mol=1000mmol =1000000µmol = 1000000000nmol

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Laboratory test results were reported in mg/100ml or µg /100ml

The formular mmol /l = mg/100ml x10/ molecular weight of substance    is used for

the conversion of laboratory results expressed in mg/100ml to mmol/l that is,

Mmol/l = mg/100ml x10/ Molecular weight of substance

Exercises: convert the following units of glucoe in mg/100ml to mmol/l

1. 2oomg/100ml 
2. 180mg/100ml 
3. 500mg/100ml

Submit your answers to me. Please if you have any difficulty, do not hesitate to 
let me know about it

WELCOME TO MLT 206 LECTURE TWO

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