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I am supposed to get a lithium blood level test tomorrow.  But I can't remember my doctor's instructions (it's either cognitive impairment or I'm just plain stupid).  How many hours after I take my last dose am I supposed to get the test?  12 to 14 hours? Or is it 10 to 12 hours?  And am I allowed the eat/drink before the test? Any help is gratefully appreciated.

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No restrictions on food or liquid intake just stay normally hydrated.


Unless you are having other tests done too.  I had my first one yesterday.  They stole seven vials of blood from me after I had been fasting for 12 hours.

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this is a big important piece of information.  would think drs, the blood lab people would know this. would think they would send me away and tell me to come back.

they ask what time i took the lithium. i had figured they calculate the level based on that amount of time, why else would they ask, write it down, and go ahead with drawing blood, if the results would then be inaccurate/unuseful?

i don't doubt this twelve hour thing, i just am agape slightly that it (seems) common practice to test the level 'whenever'. i was already getting antsy, bugging pdoc about my next levels, he said 'every six months' (one test on 300mg, then again on 600mg - but no second check on the accuracy of that) and now i discover the levels i've taken are probably not even accurate?? if they've been measuring them too high, then i probably don't have enough in my system? arg.

but if they're testing to get a good level at twelve hours, then .. um doesn't that increase the risk of toxicity? cause at four and a half hours it would be far higher, and possibly too risky for the liver etc etc.

i'm kind of confused. sorry. i'll be asking my dr. next appt. have to bug him for a req.

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Heya cj2, PJ, et al,

No idea how I missed your posts, sorry!

We docs are supposed to tell you twelve hours after your last dose.  No excuses for docs omitting that.

Lab techs vary also.

Trough levels are the routine for *most* therapeutic drug monitoring, b/c of the need to assess steady-state blood levels (as A.M. mentioned).  Also b/c that's how the standard levels have been determined, so that's what we're comparing.

At least, that's what a hematologist told me once.  FWIW.

And if there's any concern re. toxicity, symptoms or whatever, we'll get a level right away and base treatment on *that.*

And there's usually a space for your doctor to write in; here it's a small box labeled "Additional clinical information."  I use it to write in the drug dosage and timing, and any other docs I want the results copied to.

Computerized order entry systems demand a time of last dose.

Some docs are idiots.  Or tired or cranky or distracted.  Or all four.

Sorry about that.



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