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Drawing Labs from IV Line


Specializes in ER, Medicine.

Q: What's the easiest way to explain to a patient that you cannot draw blood from their IV line? Usually these lines don't give back blood and trying is futile. I generally explain that a smaller gage IV is placed and pulling back on the line causes the vein to collapse from the pressure, thus no blood return. But this is like talking in tongues. Any easier explanations?

You can say that it will clot off and you will have to be stuck with another needle to restart it and maybe more than once and then you will have to be restuck for the lab and sometimes the lab is not correct. Usually this works because they don't like to be stuck several times.

I'd probably talk about fibrin tails.

bill4745, RN

Specializes in ICU, ER. Has 15 years experience.

You can also mention that the blood sample can be contaminated by meds and/or fluid that was infused into the IV.

littlemammanurse, BSN, RN

Specializes in PP, Pediatrics, Home Health.

You can also tell them that you don't want to blow their vein, I have seen it happen!

GHGoonette, BSN, RN

Specializes in PACU, OR.

Blood samples cannot be taken from an IV line because the results will not be accurate.

Explain that it is in her best interest for her doctor to get accurate results so that he can treat her appropriately.

BrnEyedGirl, BSN, MSN, RN, APRN

Specializes in Cardiac, ER. Has 18 years experience.

I think the biggest problem with this is that blood is drawn from IV lines on occasion and people don't understand why it can't be done again. I work ER and will often try to draw from a new line,..less than an hour old, after that I explain that once the line has been in awhile it often won't give blood without blowing the vein,..hence another stick.

I've drawn blood from IV lines since I've been a nurse. Rarely have I had any problems.

gonzo1, ASN, RN

Specializes in CEN, ED, ICU, PSYCH, PP. Has 18 years experience.

I too draw blood from IV lines, and see many nurses do it. I look forward to seeing the replies to this. Maybe I need to stop this practice.


Specializes in PICU now, Peds and med-surg in the past. Has 7 years experience.

In my job with the pediatric population we do try to draw from existing IV lines whenever possible. These's little ones are tough sticks for size of vein, amount of veins you can find and also it's difficult to hit a moving target! We find on my unit that when running IV fluids are stopped about 5 minutes before, a good flush is given and an adequate waste is taken we get reliable results. This is a daily practice in all of our pediatric and PICU units. Of course, as IVs get old or in smaller gauge IVs or with IVs in the smallest veins there are times it just doesn't work. 8/10 I am able to successfully draw off of a 22 gauge or larger -24s are also possible in the right conditions. Parents are usually quite understanding when we explain why it sometimes won't work and appreciate us trying first. Now back in my adult nursing years I never drew off of IVs.


Specializes in acute care med/surg, LTC, orthopedics. Has 5 years experience.

I too draw blood from IV lines, and see many nurses do it. I look forward to seeing the replies to this. Maybe I need to stop this practice.

I have never in my whole 5 years of practice done this, or seen it done, for the very reason Bill and Goonette replied: potential contamination of blood sample.

Anyone know of best practice on this?


Specializes in ER. Has 15 years experience.

in the ER, we draw off lines - we waste, then draw. Not blood cultures, though. If it doesn't work, then we draw the old fashioned way, but if we can get blood off and not ruin the line, we get it.


Specializes in Oncology; medical specialty website.

We try to draw off a new start if possible; onc. pts. don't have many veins to work with so we try to save them sticks whenever possible. We did the same thing when I worked in the ED.


Specializes in Emergency.

theres no contamination if 5ml are wasted from PIV lines... I always draw from existing lines...

As an E.D. POC tech who has to draw 2nd & 3rd Biomarker samples oneself, I always use existing lines wherever possible (with proper waste, & flush). Sometimes it's not possible. Sometimes I have to ask the tech for that area to try to get a usable sample. Sometimes it's necessary to call Lab to ask for a Phlebotomist, for a 'difficult stick.' And, sometimes, that doesn't work, either.

i've seen a lot of hemolyzed samples from drawing off lines, but maybe the lines were already old.


Specializes in Emergency.

the trick to prevent hemolysis is not to draw with too much negative pressure. If its not drawing with a 10cc syringe, step it down to a 5, and if that doesnt work go down to the 3cc syringe... i rarely have problems drawing off existing lines.

Esme12, ASN, BSN, RN

Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma. Has 41 years experience.

Drawing off PIV line is common practice in many areas of the country. The key is to minimize the risk of hemolysis. I have found gently appling the tourniquet a good distance up the arm and not too tight. Prep the saline lock w alcohol and to use the adaptor and vacutainer just as if you were sticking the needle in the vein. If there is no return sometimes you can get a syringe and gently pull back but the risk of hemolysis increases. If all else fails you still need to do a needle stick but at least the patient knows you tried!