is there any difference in glucose in venous and capillary blood ?

We test blood sugar at home using a glucometer . The blood is collected through a finger prick.This blood comes from a capillary,and whole blood is used to measure glucose. Whereas in a lab. blood is collected from a vein and glucose estimation is done using serum.

So there is difference in source of blood as well as samples to be tested.

Will it affect the diagnosis and/ or management of diabetes ?

12 Replies

  • plasma glucose will be 10 to 12 percent higher than whole blood glucose

    lab value is measuring and reporting plasma value [or even serum] .

    doesn't matter..

    the guco meter gives a plasma calibrated value.

    this it can do with out error,


    the electro chemistry of

    the strip just presents a potential

    that is proportional to the concentration of glucose in blood.

    that far is clear enough.

    veinous blood

    differs from the

    capilary blood slightly .the percentage diference

    i am not able to give.

    [it is said the diference is least for fbs ,almost unnoticeble, and highest for ppbs . ?]

    but some people advise to slightly warm up the palms and also

    shake the hand a few times before taking sample to tide over the difference.

    [interstitial fluid]

    mr mappilli may be able to help , to throw light into this.


    we can calibrate the glucometer with the special solution they give[once in a while]

    as well as


    -taking blood tests simultaneously ,

    ie a lab test and a capilary test at the same time.

    good luck

  • i will clarfy further

    whole blood is just the entire blood you remove for test.

    if you remove the solids like red cells you get the plasma.

    in layman language the water of the blood.

    plasma is less in volume.


    in one deci litre for instance ,after removal of solids it will not be one decilitre.

    that is how the concentration of glucose rises in plasma.

    not an actual rise,.

    but our manipulation generated it.

    only in a gluco meter whole blood is measured,.

    in lab ,always plasma or serum is used.

    serum is fibrinogens also removed from blood.

    they dont make much difference.

    that is plasma and serum.

    as far as glucose is concerned.

    blood=plasma +solids like red cells etc.

    serum=plasma minus fibrinogens.

    as far as a glucose measurement is concerned,

    for lab people-

    they just dont make a difference.

    and in a glucometer

    basicaly only the glucose goes into reaction with the enzyme in the strip.the electro chemistry then produces the electron transfer in the pair of electrodes in the strip ---

    finally the microprocessor programs compute the conentration of glucose.

    thus plasma calibration is only a presentation of numbers.

    it has to tally with the lab values where they centrifuge the blood and pippet the plasma out.

    however the meter has to be calibrated routinely with a solution or with lab comparison as venkatji has pointed out.

    finger prick blood is more similar to arterial blood,

    i read elsewhere.[?]

    that looks agreeable because no one can prick a vein or artery so acurately in a micron will be a mixed up blood.mostly arterial[?]these fine details i am not sure.


    fbs will tally in case with capilary blood and venous blood. ppbs can make differences.

    good luck

  • To my knowledge,the results differ,The serum readings will be slightly higher by about 10 points.It is generally advised that glucometer readings may not be used for clinical purposes.Also,to be sure,both methods can be used at the same time once in a while to calibrate the glucometer according to the lab results.

  • There is small but significant difference in the blood glucose results analysed on a bedside glucometer when the samples are taken from capillary or venous sources. Caution must be exercised in accepting the results as equivalent or using either as substitute for a laboratory blood glucose results.

  • that article cited is wrtten some 12 years ago.

    modern plasma calibrated meters came up much later than that.


    in those days they were employing strip bio chemistry

    different from present day one.[the electro chemistry and measuring a potential difference]

    even at that time the mean diference is only 0.61 in terms of mols -that works out to aproximately 10 mg per dl.

    multiplying 0.61by 18.[ 7.66 minus 7.05=0.61 ]

    why should there be diference between

    capilary blood and venous blood ?though the heart beats 72 times per minute.enough opportunity for circulation.?interstitial fluids?no, says some reports [?].

    i will leave the question open.

    best thing is to compare glucometer once in a while with reliable lab values or a test solution.

    good luck

  • Even at that time glucometers were plasma adjusted,so there is no confusion about that.

    It is also almost universally accepted that there is no variation in basal or fasting blood sugar, whether blood is from capillary or a vein. It is only in post meal that there is some difference in blood sugar reading . The whole blood from capillary shows higher bs reading by approx. 10% than the bs estimated from plasma,(lab. Test using blood from a vein ).

    The reason is easy to explain,if there is need.

  • dear patliputra,

    i was under the impression that

    plasma adjusted glucometers began comming

    during the last 10 years. that is 2005 onwards..

    but that article written in 2003.

    setting that aside ,

    what i do want to point out is that the modern glucometer

    mesures the plasma glucose only.

    or in other words it just measures the

    blood glucose.

    it is dificult for me to prove what i say--

    but i will put it this way.

    the modern electro chemical gluco meter

    just acts on the glucose alone --

    in other words

    you construct two samples-

    1)from the capilary whole blood sample you just remove the solids and generate a plasma

    2]take the whole blood capilary blood itself

    both these two samples above will give the same result in a modern glucometer using the presentday electro chemistry of the strips.

    .in my scientific past life,

    i always did this type of conversion to an experiment--

    though it was safer to remain within arguments, personally speaking!!!

    difficult to believe?

    but it is true.i will not try to prove it.

    because it is too much going into the so called


    it is also possible, by rare chance,

    my understanding of the electron transfer in between the electrodes in the strip may be at error.

    in which case the meter will read differently.

    the other thing that fbs will tally with venous and the capilary is easy to understand -

    because ,dietary glucose not arriving ,

    a stable venous and arterial glucose is built up.

    but in ppbs dietary glucose appearing in the 'portal vein' takes time to dissipate throughout the arteries and veins constituting a difference in capilary to venous blood.


    these things above are just my understanding only and not like my usual

    presentations where i try to reach university level descriptions.

    i pointed out earlierin my first response.


    fbs will tally in case with capilary blood and venous blood. ppbs can make differences."

    thanks for the response anyway.

    good luck

  • Dear Indiacratus, the para in reference was published in 2005.

  • that is true about publication. but the research paper was written much earlier=it was accepted in 2003 means the research done much earlier.

    "Correspondence to:
 Dr R Boyd
 Emergency Department, ------------------

    Accepted 3 December 2003"


    leave alone that.

    what i said about the chemistry within the modern meter

    i will not be able to translate to practice

    with out further clarifications


    reasoning purely on the

    chemical reaction can go wrong in practice,.

    to come out of it , a lot of study may have to be done, which i am unwilling.

    in other words

    however accurate is my understanding of the chemical basis behind the meter may be,

    in practice there could be descripancies.

    we hve to leave the discussion here.

    good luck.

  • Thank you.

  • The blood sugar from capillaries and veins does not matter when taken for the management of blood sugar.Difference of 10 to 20 percent does not matter.Secondly,the range of FBS and PP ranges are arbitrarily fixed,which were different from time to time. The international range was first fixed at 135 mg/dl which has changed from time to time and now it is below 100 mg/dl.This way it has been estimated that nearly 60% Indian population suffers with diabetes. All is arranged by pharmaceutical companies to sell their products.This causes depression and the level increases.So my advice is take it lightly till there is level beyond 200 mg/dl

  • Precisely said without any room for doubts. Well.

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