DNR on a lab report stands for “did not run,” meaning the laboratory did not perform that particular test. It has nothing to do with the more widely known medical abbreviation “do not resuscitate.” When you see DNR next to a test name, it almost always means something went wrong with the blood sample before the analyzer could process it, so the lab could not produce a reliable result. The reasons range from a clotted specimen to not enough blood in the tube, and the fix is usually straightforward: a new sample needs to be drawn.
Why a Lab Would Not Run Your Test
Laboratories reject specimens when something about the sample makes the result untrustworthy. A test run on a damaged or compromised sample could spit out a number that looks real but is dangerously wrong, so labs flag it as DNR rather than report a misleading value. The rejection protects you, even though it feels like an inconvenience.
A systematic review and meta-analysis of blood specimen rejection across clinical laboratories found that the leading causes of rejection were clotted specimens (about 32%), hemolysis (about 23%), insufficient volume (about 23%), and labeling errors (about 7%).1Practical Laboratory Medicine. Blood specimen rejection rate in clinical laboratory: A systematic review and meta-analysis – Section: Results In other words, the vast majority of DNR results trace back to something that happened to the blood between the moment the needle entered your vein and the moment the tube reached the analyzer. The lab’s chemistry and equipment were ready; the sample was not.
Clotted Specimens
Clotting is the single most common reason labs reject a blood sample. Most hematology and coagulation tests require liquid, unclotted blood, which is why certain tubes contain an anticoagulant (like EDTA or citrate) to keep the blood fluid. If the blood clots anyway, it alters cell counts, traps platelets, and consumes clotting factors, making any result from that tube unreliable. When samples clot before analysis, they are rejected, which delays treatment decisions and can require repeated sampling.2PubMed. Clotted blood samples in the neonatal intensive care unit: A retrospective, observational study to evaluate interventions to reduce blood sample clotting – Section: BACKGROUND
How often does this happen? At one large emergency laboratory that tracked rejections across a full year, fibrin clots accounted for 28% of rejections for biochemistry tests and 35% of rejections for coagulation tests.1Practical Laboratory Medicine. Blood specimen rejection rate in clinical laboratory: A systematic review and meta-analysis – Section: Results In hematology labs specifically, one study found that clotted samples accounted for over 86% of all specimen rejections for routine hematology tests.3PubMed Central. Pre-analytical Factors Influencing Blood Sample Rejection Rate in the Hematology Laboratory of the Philippine General Hospital from 2018 to 2022: A Cross-sectional Study – Section: RESULTS Clotting can happen for several reasons: the tube wasn’t mixed gently enough after collection, the draw was difficult and slow (giving the blood time to start coagulating), or the sample sat too long before processing.
Hemolysis, Low Volume, and Other Sample Problems
Beyond clotting, a few other specimen issues frequently trigger a DNR flag.
- Hemolysis: Red blood cells rupture and release their contents into the surrounding fluid. This floods the sample with potassium, lactate dehydrogenase, and hemoglobin, which can falsely elevate or interfere with dozens of common tests. Even mildly hemolyzed specimens can throw off results for electrolytes, liver enzymes, and cardiac markers. Modern analyzers detect hemolysis automatically by measuring how much free hemoglobin is in the sample using light at specific wavelengths.4PubMed Central. Educational Case: Hemolysis and Lipemia Interference With Laboratory Testing – Section: How Are Hemolysis and Lipemia Detected and Quantified? If the level exceeds the threshold for a given test, the result is suppressed and you see DNR instead.
- Insufficient volume: If the tube doesn’t fill enough, the ratio of blood to anticoagulant or preservative gets thrown off. This is especially critical for coagulation tests like PT/INR, where the citrate-to-blood ratio must be precise. The lab will reject a short-draw tube rather than report a skewed result.
- Lipemia: Extremely high lipid levels (often visible as milky-looking serum) scatter light in the analyzer and interfere with many assays. Like hemolysis, lipemia is automatically graded by instruments using spectrophotometric readings in the 660 to 700 nm wavelength range.4PubMed Central. Educational Case: Hemolysis and Lipemia Interference With Laboratory Testing – Section: How Are Hemolysis and Lipemia Detected and Quantified? If lipemia is high enough to compromise a particular test, that test goes to DNR.
- Labeling errors: If the tube lacks proper patient identification, or if the label doesn’t match the requisition, the lab cannot legally run the sample. This is a patient-safety measure: running a misidentified specimen risks attaching someone else’s results to your chart.
All of these fall under what lab professionals call the “preanalytical phase,” meaning the stretch of time before the sample actually reaches the analyzer. When one group documented over 46,000 lab errors (excluding minor hemolysis), 97% of them occurred in this preanalytical window.5Clinical Chemistry. Preanalytical Phase Errors Constitute the Vast Majority of Errors in Clinical Laboratory Testing – Section: Results The instruments themselves are rarely the problem. The weak link is everything that happens between the needle and the machine.
How Modern Labs Catch These Problems Automatically
You might wonder how the lab even knows your sample is hemolyzed or lipemic before running the test. Most high-volume clinical chemistry analyzers now perform an automatic quality check on every sample before analysis begins. They shine light through the serum or plasma at multiple wavelengths and generate what are called “serum indices” for hemolysis, icterus (bilirubin), and lipemia. This automated detection is more reproducible than the old method of a technologist visually inspecting each tube, and it catches mildly compromised specimens that the human eye would miss.6Biochemia Medica. Hemolysis detection and management of hemolyzed specimens – Section: Automated processing
Laboratories then build automated decision rules around these indices. If a sample’s hemolysis index exceeds the interference threshold for, say, potassium, the system suppresses the potassium result and flags it as DNR, but it might still report the sodium from the same tube if sodium is unaffected at that hemolysis level.7PubMed. Developing optimized automated rule sets for reporting hemolysis, icterus and lipemia based on a priori outcomes analysis – Section: METHODS This is why you sometimes see DNR next to one test in a panel while the rest of the panel reports normally. It doesn’t mean the whole draw was wasted; it means one particular assay couldn’t tolerate the level of interference present in your sample.
What DNR Means for Your Care
When a specimen is rejected and a test flagged DNR, it does have a real downstream effect. Sample rejection prevents analysis, increases the time it takes for results to come back, and can delay diagnosis and treatment.8Practical Laboratory Medicine. Blood specimen rejection rate in clinical laboratory: A systematic review and meta-analysis – Section: Discussion If you are in a hospital and your morning labs come back with a DNR on your potassium, for example, your care team has to order a redraw, wait for the new sample to be collected and transported, then wait again for it to be processed. In an emergency setting where a physician needs a coagulation result before starting blood thinners or performing a procedure, that delay can matter.
For outpatients who notice DNR on a result sent through a patient portal, the practical impact is usually a phone call from the clinic asking you to come back for another draw. Annoying, but not dangerous. The key thing to understand is that DNR is not a clinical finding about your health. It is a process notation. Your blood wasn’t abnormal in any medically meaningful way; it just wasn’t in a condition the lab could trust for that specific test.
The “Do Not Resuscitate” Confusion
The anxiety people feel when they see DNR on lab results is understandable. In most medical contexts, DNR means “do not resuscitate,” a legal directive about end-of-life care. Seeing those three letters on a lab report can be alarming if you don’t know the lab-specific meaning. This kind of abbreviation confusion is not rare in medicine. A survey asking healthcare volunteers to interpret 20 common medical abbreviations found that the average score was only about 32%, and 75% of the abbreviations tested had one or more alternative definitions.9PubMed Central. Interpretation and Misinterpretation of Medical Abbreviations Found in Patient Medical Records: A Cross-Sectional Survey – Section: Results Medical shorthand is full of overlapping acronyms, and context determines which meaning applies. On a lab report, DNR is always “did not run.”
Some labs use different notations to avoid this exact confusion. You might see “TNP” (test not performed), “QNS” (quantity not sufficient, meaning not enough blood), “CANC” (cancelled), or simply a comment like “specimen clotted” or “hemolyzed specimen” spelled out in the notes field. If your lab report uses any of these, the underlying message is the same: that particular test was not completed.
When Children’s Samples Are More Likely to Be Rejected
Pediatric blood draws present a heightened challenge for specimen quality. Smaller veins, smaller collection volumes, and the difficulty of keeping a child still during a draw all increase the odds that something goes wrong before the sample reaches the lab. A systematic review of preanalytical errors in pediatric blood sampling, covering over 110,000 samples, found that the most common problems were inappropriate blood volumes in tubes, sample clotting, use of incorrect tubes, and contamination.10Türk Biyokimya Dergisi / Turkish Journal of Biochemistry. Preanalytical errors in pediatric blood sampling: a systematic review of common challenges and risks – Section: Results
For parents, this means that seeing DNR on a child’s lab results is somewhat more common than in adults and almost certainly reflects a collection difficulty rather than anything about the child’s health. Neonatal samples are especially vulnerable because the volumes drawn are tiny, making even a small shortfall enough to push the sample below the minimum volume the analyzer requires. Redraw requests in pediatric settings are handled carefully, since clinicians want to minimize the number of needle sticks a child endures, but sometimes there is no alternative.
The Hidden Cost of Rejected Specimens
Rejected samples are not just a minor operational hiccup. They cost real money and real resources. A study at a tertiary pediatric hospital estimated that the annual cost of preanalytical errors was about 74,000 euros for roughly 54,000 blood drawings. About 60% of that cost was personnel time, with additional costs from extended hospital stays, repeat laboratory analyses, and materials.11PubMed Central. Direct costs of blood drawings with pre-analytical errors in tertiary paediatric hospital care – Section: RESULTS Per draw, the cost of errors came to roughly 1.4 euros, which may sound small in isolation but scales fast across a hospital system handling thousands of draws daily.
For the patient, the cost is often indirect: extra time at the clinic, another copay if you are an outpatient returning for a redraw, and the discomfort of another needle stick. In inpatient settings, it adds up to extended uncertainty about diagnoses and, in some cases, longer hospital stays while clinicians wait for results they need before making decisions.
How to Reduce Your Chances of a DNR Result
Most of the factors that lead to specimen rejection are outside your control as a patient. You cannot prevent a tube from clotting if the phlebotomist’s technique was the issue, and you cannot stop your red blood cells from hemolyzing if the draw was traumatic. That said, a few things are within your influence.
Staying well hydrated before a blood draw makes your veins easier to access, which leads to a smoother, faster draw with less tissue trauma. A quick, clean venipuncture is less likely to produce a hemolyzed or clotted sample than a difficult stick where the needle has to be repositioned. If you have small or hard-to-find veins, mention it to the phlebotomist so they can plan accordingly, perhaps using a butterfly needle or drawing from a preferred site you know works well.
If you are managing a condition that requires frequent lab monitoring, like diabetes or anticoagulant therapy, and you keep getting DNR results, it is worth asking your provider whether there is a pattern. Repeated clotting in coagulation tubes, for instance, could point to a collection technique issue that a different phlebotomist or a different draw site might resolve. The lab itself often tracks rejection rates and can identify if a particular collection point has a recurring problem.
Other Abbreviations You Might See Alongside DNR
Lab reports are full of shorthand, and DNR is just one of several notations that signal something unusual. Knowing a few others can save you a worried phone call.
- QNS: Quantity not sufficient. The tube did not contain enough blood for the test. Same outcome as DNR, but with a more specific explanation.
- HEM: Hemolyzed. The sample showed red blood cell breakdown. Some labs use this as a flag alongside a result that was still reported but should be interpreted with caution; others use it to explain why a result was suppressed.
- LIP: Lipemic. The sample was visibly fatty, which can interfere with certain assays.
- ICT: Icteric. The sample had elevated bilirubin, which gives serum a dark yellow or greenish tint and can interfere with some colorimetric tests.
- TNP: Test not performed. Functionally identical to DNR, just a different lab’s preferred abbreviation.
These flags exist because labs would rather tell you a test was not completed than hand you a number that might be wrong. A missing result you can repeat is far safer than a false result that leads to an incorrect treatment decision. If you see any of these on your report and are unsure what happened, your provider’s office or the lab itself can usually clarify in a quick phone call what went wrong and whether you need to come back for a new draw.