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Any idea what could cause low Osmolality with normal Calcium(NA+) levels?
Peter_V posted:
A recent blood test showed a low measure Osmolality of 273 with NA+ 140, Glucose 111, and BUN 19

6 months ago I had similar results Osmolality 270, NA+ 139, Glucose 111, BUN 14

I'm a diabetic and I'm managing it pretty well with diet, exercise and Metformin. According to my meter, fasting glucose levels are generally under 100.
Other than the diabetes my only current symptoms are muscle pain that lasts for several days after exercising, and occasionally graying out when standing up.
BP is typically around 118/73
Meds I'm taking:
Metformin 850mg twice a day
Adderal XR 15mg daily (I also have ADD)
And 2.5mg Lisinopril and 82mg Asprin as prophylactics

Oh yeah my MCV dropped from 84 last year to 83 on a recent blood test which is below the normal range listed on the results (84-92)

I have an appointment in a couple weeks to discuss this with my doctor, but I was wondering if this was anything to be concerned with.
DavidHueben responded:

Your osmolality is not that low. It is just barely out of the "normal range" of 275 - 299. And your MCV is also just one point below the "normal range". I know my doctor would not give either a second thought.

All your other lab results are normal, with the exception of your fasting plasma glucose level of 111. A few less carbohydrates might fix that.

I would not worry about anything.

Watch what people are cynical about, and one can often discover what they lack. - General George Patton Jr
nwsmom responded:
Peter, the "normal" range is defined as where 95% of the normal (i.e., healthy) population will fall. That leaves 5% to be a little higher or lower, and still perfectly "normal". Don't panic over such minimal variations from the norm: they are probably within-run and run-to-run variation.
Peter_V replied to nwsmom's response:
I'm not panicking, not even greatly concerned about the BT results.

I'm concerned about almost blacking several times a day when I stand up and I'm bothered about my muscles hurting for days after exercising (mostly because it impacts the amount of exercise I can do)

I probably didn't express myself very well, but the main reason I was asking was to see if these BT results might have anything to do with these two symptoms.
Peter_V replied to Peter_V's response:
Oh yeah, the other thing I was interested in is how the osmolality can be low when the other measurements (NA , etc.) are normal or high

The calculate osmolarity is supposed to be fairly close to the measure osmolality, but in my case the calculated level is 20 points higher.

I've read that if measured is higher than calculated by more than 15 points this is a serious problem.
But I couldn't find anything that described why the measure would be that much lower than calculated.

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