High blood sugar levels - how long before dangerous?

If your diabetes has been diagnosed before you have started to develop complications you do get a bit of a run up to avoiding complications by reducing your levels to safe numbers by altering your diet.

I'm T2, but high blood sugar levels are toxic and have the same impact on all diabetics. I can't comment on insulin use as I don't use it.

My own experience is that running blood sugars above a normal level and below 9mmol, even just for an afternoon, gives me headaches and affects my concentration. I ate 2 very small pieces of very nice bread with my lunch last Wednesday (spread with a very ripe Brie) and it left me headachy and fuzzy headed all afternoon :?

I was diagnosed thanks to an anxiety attack and chest pains at the end of January - a cardio check up confirmed that I don't have any sign of cardiovascular disease. The other blood work confirmed I have diabetes. I've been checking my blood sugar regularly since May and I don't like to go over 7 after eating (or at any time really) and I'd be happier much lower.

Those post prandial spikes do have a fairly quick impact on me.

Since I got my HbA1c down from 7.8% to 6% I have noticed a difference in my feet, about 3 months ago I noticed a slight loss of sensation. The sensation seems to have improved recently, although this may simply be that I have also lost weight.

I'd agree that even short term high levels are not good for us, especially if they occur every day.

To give a short answer,(and sorry I'm not an expert!) I don't think we actually know! Though most people would suggest that the fewer high blood sugar excursions the better.

The biggest short term danger from high blood glucose levels is DKA. At 15mmol you should perhaps be checking for ketones and correcting to bring the levels and any ketones down.
However 10 until very recently was the top bracket of postprandial targets, most authorities now give a lower figure.The UK after meal type 1 target is now a maximum of 9 mmol. I

I'm not certain there has been any long term research into the effects of day to day variations or odd incidences of hyperglycaemia. It is all pooled together to show the effects of overall control.
Much of our data on complications comes from the DCCT
The DCCT trials showed that elevated HbA1cs over time are directly correlated with complications. The higher the average HbA1c the sooner the likelihood of complications (particularly microvascular).
http://www.dgdiabetes.scot.nhs.uk/icp/icptype2/hba1ctargets.shtml

A 2008 reanalysis of the data suggests that variable HbA1cs, that is short-term glucose instability can have an adverse effect.
http://www.ncbi.nlm.nih.gov/pubmed/18650371?dopt=AbstractPlus

Obviously to have a consistently lower HbA1c it is necessary to have lower overall levels but the odd higher level, brought down quickly wouldn't be reflected in the HbA1c. (My HbA1c is consistently in the 5s and I rarely go above 8mmol but it does sometimes happen)

recent studies have found high er post prandial levels to be predicitve of CV events in type 2 but I've found nothiing directly on type 1.
http://diabetes.diabetesjournals.org/content/54/1/1.abstract
http://jcem.endojournals.org/cgi/content/abstract/91/3/813

As stated, it's hard to know exactly and so I would recommend to any diabetic to use a hard-line approach;

If your glucose levels are greater than 6mmol then damage is being done to your body. Doesn't matter if it's for a day or an hour, but obviously the longer the period, the longer your body is exposed to dangerous levels.

Hi Tony G

As posted by phoenix and acron it’s difficult to quantify with any specific time frame "high blood sugar levels - how long is dangerous", with the exception of diabetic ketoacidosis (DKA) which can occur in hours.

Do high blood glucose levels always lead to complications? John Walsh’s excellent book “Using Insulin” states “Not always - occasionally (and he stresses occasionally) someone escapes serious health complications despite a long history of poor control.”. However Walsh continues “it is rare to find no damage at all when blood sugars have remained persistently high over several years”.

Cholesterol levels, genetics, nutrition, exercise, blood pressure, smoking, alcohol intake, hormone levels, vitamin & mineral balance and stress also all play a role in determining the extent of damage.

Early detection of the potential complications of diabetes also plays a significant & crucial part in reducing long term complications – many people in the UK with diabetes for example persistently fail to attend for Out Patients Appointments – one example is eye screening – the screening is there for a reason!!
Early detection of potential complications to eyes. kidneys, heart & nerves and thus intervention can also prevent significant damage.

Tight glycamic control as tight as you can get it plus screening are significant factors in reducing the dangerousness associated with high blood sugar levels.

Best wishes

Txx

in reply to acron, i measured two friends about 30 mins after a curry on sat night, both healthy and one extremely fit, and both had BG's of over 6 (6.3 & 6.8). not sure how long they stayed up there for but when i measured my own BG it was 5.4 so it got me thinking maybe my targets post meals are a bit strict. personally i don't like to hang around above 6 normally but if damage is done above this then are you suggesting most non-diabetics are causing damage on a daily basis whenever they go beyond 6?

my consultant rekons if a 'normal person' drinks a bottle of lucozade they could hit 8. not sure i agree with that but i might try it on the gf.

howie

Howie, I agree with you,
you might like to look at this presentation. It is a small study using continuous monitoring on healthy, young people without diabetes.
Slide 17 is a graph showing all the results.
http://www.diabetes-symposium.org/index.php?menu=thumbs&source=&sourceid=0&id=322
6mmol is 108mg/dl, you will see that very may of the postprandial spikes were well above this.
the mean after breakfast was 132mg/dl (7.33)
the mean after lunch was 118 (6.6)
the mean after dinner was 123 (6.8)
There was obviously a fair amount of variability so some people on some meals were 150, (8.3)

For people with type 1 we are also using less than perfect tools for insulin delivery. There may be a danger for some people in aiming too low at 2 hours. The peak action of rapid insulins continues past this 2 hour point, too low readings at 2 hours may result in a hypo at 3.