How to Read a TEG: Clot Strength and Lysis

What You’ll Need

The complete TEG report, including the graph, numeric results, reference ranges, and any test-specific notes.
Relevant context from the ordering care team, such as why the test was performed and whether the sample was run with a special reagent or medication-specific assay.
A clinician trained to interpret coagulation testing. TEG is a specialized test; this guide explains its common features but cannot determine what treatment someone needs.

Step-by-Step

Confirm which test you have. Check that the report is for thromboelastography, not a different test with a similar abbreviation. TEG instruments and assay types can report different parameters. Some reports include standard TEG, heparinase, platelet-mapping, or other channels; do not apply one assay’s interpretation to another.
Read the laboratory’s reference intervals first. Find the ranges printed beside each result and note any flags. Reference intervals can vary by instrument, reagent, sample type, and lab. A value marked high or low is not, by itself, proof of a particular disorder or a direction to give a blood product.
Orient yourself to the tracing. A typical TEG graph plots clot firmness over time. It begins near the baseline, opens as clotting starts, widens as the clot gains strength, and may narrow later if the clot breaks down. The horizontal axis represents time; the vertical movement or width represents clot firmness, though display conventions may differ. Look at the report legend.
Check clot initiation. The reaction time, commonly labeled R, is the interval until the tracing first reaches the instrument’s threshold for clot formation. A longer R can indicate delayed initiation in that test context; a shorter R can indicate faster initiation. Consider the assay, reference range, medications, and clinical setting before drawing conclusions.
Assess how quickly the clot builds. The clot-kinetics time, often K, measures progression from initial clot formation to a specified firmness. The alpha angle describes the rate of clot strengthening. A longer K or smaller angle may point to slower strengthening, while a shorter K or larger angle may point to faster strengthening. These related values should be considered together, not as isolated verdicts.
Review maximum clot strength. Maximum amplitude, or MA, is the greatest firmness reached by the clot. It reflects contributions from platelets and fibrin, among other factors. A low or high result has multiple possible explanations; it does not identify a cause on its own. Compare it with the assay-specific range and other laboratory findings.
Look for evidence of clot breakdown. The report may include LY30, which describes the percentage decrease in clot firmness 30 minutes after MA, or another lysis measure. Check the exact label and timing on the report. A result outside the lab’s interval warrants interpretation by the care team; a flat or changing line alone should not be overread.
Put the pattern together. Summarize whether initiation, clot growth, strength, or breakdown is the main feature outside the stated range. Then review the reason for testing, recent procedures, medications, other coagulation results, and sample quality with the clinician. TEG is one piece of information, not a stand-alone diagnosis or treatment plan.

Common Mistakes

Using a universal “normal” range: Cutoffs differ among methods and labs. Use the range on that specific report, not one copied from a website or another hospital.
Calling every flagged result a diagnosis: A flagged R, MA, or lysis measurement describes a test result. It does not establish why the result occurred or what action is appropriate.
Reading one number in isolation: TEG values describe different phases and interact. A conclusion based on MA alone, for example, can miss changes in initiation or clot breakdown.
Confusing assay channels: Specialized channels may be designed to answer particular questions. Their labels and reference ranges are not interchangeable with standard TEG.
Assuming the graph tells the whole story: A tracing can be affected by collection, handling, timing, and instrument details. The numeric report and laboratory comments matter too.

Tips

Keep the report’s units, assay name, and reference ranges visible while reviewing it.
Use a simple four-part summary: initiation, clot growth, maximum strength, and lysis. This makes it easier to discuss the result without overstating what it means.
Ask the ordering clinician which specific question the test was intended to answer and how the result fits with other findings.
If comparing results over time, check whether the same assay, instrument, and lab method were used. A numerical difference may not be directly comparable across methods.
Do not change prescribed medicines or make decisions about transfusion or other treatment based on a TEG report without the care team.

Troubleshooting

The graph is missing or hard to read: Check whether the report has a second page, a separate tracing view, or a legend explaining its axes. Ask the lab or ordering team for a readable copy rather than guessing from a cropped image.

There are no reference ranges: Ask the laboratory or ordering clinician for the method-specific intervals and whether the report is complete. Do not substitute ranges from a different instrument or assay.

The result looks inconsistent with other tests: TEG and conventional coagulation tests measure different aspects of clotting and may not match one-for-one. The care team can review timing, medications, sample quality, and the purpose of each test.

A special channel is unfamiliar: Find the assay name and its interpretive note, then ask the clinician what that channel measures. Avoid applying standard TEG assumptions to a specialized result.

The report is marked invalid, clotted, or technically limited: Treat the result as potentially uninterpretable and contact the ordering team. They can determine whether a repeat sample or another test is needed.

Frequently Asked Questions

What does TEG stand for?

TEG stands for thromboelastography. It is a laboratory method that tracks changes in clot formation and firmness over time.

What is a normal TEG result?

There is no single range that applies to every TEG method. Use the reference intervals printed on the report and ask the ordering clinician to interpret them for that assay and situation.

What does a high MA mean?

MA is maximum clot firmness, influenced by platelets and fibrin. A high value describes stronger firmness in that test, but it does not by itself identify a cause or establish a diagnosis.

Does an abnormal TEG mean I have a bleeding or clotting disorder?

Not necessarily. An out-of-range result can have several explanations and must be assessed alongside symptoms, other tests, medications, and the reason for testing.

Can I interpret a TEG result without a clinician?

You can learn what the labels describe, but the result should be interpreted by a clinician familiar with the assay and the patient’s context. Do not use it alone to make treatment decisions.

Is TEG the same as a standard clotting blood test?

No. TEG measures the evolving firmness of a clot in a sample, while standard tests measure other parts of coagulation. They provide different information and are not interchangeable.

Further reading: American Society of Anesthesiologists. Details can change, so check the official page for anything that matters to you. Spotted a mistake? Tell us. How we write an answer.