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Why does high blood sugar make diabetics sleepy?

Discussion in 'Current Medical Students' started by brianfall, Jun 8, 2009.

  1. brianfall

    brianfall New Member

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    Maybe I should know the answer to this by now - but..
    Why does high blood sugar make people with diabetes sleepy?

    I know that high blood sugar is a sign of insulin deficiency or resistance... but... I'm interested in the effect going the other way.

    I mean I know that... insulin deficiency/resistance = poor utilization of blood glucose = tiredness, I get that. But what about if a diabetic requires the same amount of energy as they would normally, has the same insulin levels as they would normally, but just eat more cake?

    Why is it that raising the blood sugar level per se increases tiredness, irrespective of how much energy that person needs?

    Any thoughts gratefully received!
     
  2. Spencer Wells

    Spencer Wells Noodly Doctory Moderator

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    I'm not convinced that hyperglycaemia per se results in tiredness. If I were to inject myself with 50mL of 50% glucose my blood sugar would go up, but I'm not sure I'd be tired.
    Obviously, as you've stated, the reason that diabetics with hyperglycaemia feel tired is due to relative lack of insulin, and therefore decreased intracellular levels of glucose-6-phosphate.

    I suppose that hyperglycaemia leading to glycosuria and therefore true dehydration (i.e. loss of intracellular water) would explain feeling pretty damn rotten, and the associated sodium abnormalities would lead to obtundation, and certainly even with only mild dehydration there is great fatigueability, but in the absence of this I can't think of a mechanism.

    It has been many years since I did any real biochemistry, and I'll have forgotten a lot. Meh.
     
  3. AR1972

    AR1972 New Member

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    I'm a type 1 and when i have a "mad minute" and consume an amount of "naughty food" I feel like I could sleep for a 100 years, you have to be a diabetic to experience this type of tiredness ;)
     
  4. Singh.Simran

    Singh.Simran New Member

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    I hear it is simply the osmotic consequences, so yeah, dehydration, nothing fancy.
     
  5. brianfall

    brianfall New Member

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    Thanks for the replies.

    Spencer thanks for reminding me that having high blood glucose would draw water out of surrounding cells and into the blood stream via osmosis. It would also draw water out of erythrocytes.

    This paper; IOS Press - Journal Article
    shows that dehydration;

    "caused progressive reduction of blood and plasma fluidity...elevation of erythrocyte aggregation [and that] ...oxygen transport was decreased by 18%"

    So maybe one of the reasons high blood sugar makes you feel tired is that it reduces your body's ability to transport oxygen.

    I've also read that high blood sugar stimulates secretion of somastatin which inhibits TSH. Inhibition of TSH would slow the metabolic rate and this could lead to tiredness like you get in hypothyroidism as well.

    Hmmmm.......
     
  6. melon

    melon New Member

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    I doubt this is the mechanism. Bare in mind the half-life of T4 in the body is 7 days. So a sudden drop in TSH from some obscure feedback loops wouldn't have an immediate effect.

    I'd go along with the reason you feel tired being the hyperosmolar effects of being hyperglycaemic. Thus the aptly named hyperosmolar non-ketotic coma.
     
  7. couldntgetaname

    couldntgetaname New Member

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    I had some sort of eureka moment in the library earlier when I was supposed to be revising for impending OSCE doom in the morning.

    I had a confluence of events involving decreased efficiency of alveolar transport from basement membrane thickening, and increased DPG and a bit of acidosis all causing anaemia-like fatigue thrown in on top of the dehydration already mentioned.

    Can't for the life of me recall how I made a coherent arrangement of that, which is rather irritating because I was dead chuffed [though admittedly probably very definitely wrong] at the time.
     
  8. brianfall

    brianfall New Member

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  9. couldntgetaname

    couldntgetaname New Member

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    2,3-Diphosphosomethingsomethingate.
     
  10. jaanus

    jaanus New Member

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    2,3-diphosphoglycerate, regulator of oxygen binding curve. And don't worry about not knowing things, it's much more fun to find out new things.

    PS! Don't know about diabetes, but with normal people. High blood sugar - high insuline - uptake of glycose and aminoacids by cells - less "competition" for receptors of the BBB with regard to aminoacids (less aminoacids in the blood) - more Trp to brain - more serotonin - more melatonin - sleepy sleepy. But as I said, this would be something that DOES NOT apply with diabetes, either I or II.
     
  11. bandot

    bandot New Member

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    Why does high blood sugar make people with diabetes sleepy?

    I have type 2 diabetes if I eat cake or anything containing high sugar it will put me in deep sleep for 4 hours. This does not happen if I take insulin. Oxygen reduction in the blood seems most logical.
     

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