- 01D-dimer is a rule-out test
A normal D-dimer in someone at low or moderate risk makes a clot very unlikely. A high D-dimer only says that clot formation and breakdown is happening somewhere in the body; it cannot say where, why, or whether it is a dangerous clot. That is why doctors judge the probability of a clot first and read the D-dimer second. A normal result is less reliable if you are already taking a blood thinner or have had symptoms for more than a week or two, so tell the clinician 14.
An elevated D-dimer usually does not mean a dangerous clot. D-dimer is released when the clot-dissolving enzyme plasmin breaks down cross-linked fibrin, so it only appears after a clot has formed and then been broken down 1. Your body makes and dissolves small clots all the time (after a bruise, an infection, a pregnancy, an operation), so plenty of people with no dangerous clot have a D-dimer above the line. The test works in one direction. A normal result in someone at low risk makes a deep vein thrombosis (DVT, a clot in a leg vein) or pulmonary embolism (PE, a clot in the lung) very unlikely, and a high result is a prompt to look further 2. For the test itself, see the main <a href="/biomarkers/d-dimer">D-dimer page</a>, and for how it sits alongside PT, INR and fibrinogen, <a href="/learn/clotting-tests-explained">clotting tests explained</a>.
The marker this page is about
What counts as high
Doctors read a D-dimer only after judging your clinical probability, meaning how likely a clot looks from your symptoms and history. The same number can mean no scan is needed for one person and a scan today for another 2.
| How your report writes it | Usual cut-off |
|---|---|
| mg/L FEU | 0.5 |
| µg/mL FEU | 0.5 |
| ng/mL FEU | 500 |
| µg/L FEU | 500 |
| ng/mL DDU | about 250 |
FEU and DDU are two ways of expressing the same result, so a DDU number read against an FEU cut-off looks half as high as it is (<a href="/learn/lab-units-explained">lab units explained</a> covers unit swaps in general). D-dimer assays are also not standardized between manufacturers, so the cut-off printed on your own report is the one to read against 1.
Where an example D-dimer of 680 ng/mL FEU sits (example: a 72-year-old)ng/mL FEU
YEARS and PEGeD are checklists doctors use for a suspected PE. YEARS asks three questions: are there signs of a DVT, is the person coughing blood, and is PE the most likely diagnosis? With none of the three, a D-dimer up to 1,000 ng/mL FEU counts as negative; with any of them, the line is 500 2. PEGeD uses the clinician's overall probability instead: 1,000 when it is low, 500 when it is moderate, and straight to a scan when it is high 6.
No guideline grades a high D-dimer into mild, moderate or severe bands. What matters is which rule-out cut-off applies to you.
| Band | US units | SI units | What it usually means | Usual next step |
|---|---|---|---|---|
| Below the cut-off | Under 500 ng/mL FEU (under about 250 DDU) | Under 0.5 mg/L FEU | With low or moderate clinical probability, a DVT or PE is very unlikely 24 | If the clinician has judged a clot unlikely, imaging is usually not needed; with high probability or symptoms, imaging goes ahead anyway 2 |
| Over 50: above 500 but under your age-adjusted cut-off | 500 to age x 10 ng/mL FEU | 0.5 to age x 0.01 mg/L FEU | Counts as negative for PE when a clot was not judged likely; 0.3% had a clot within 3 months in ADJUST-PE 3 | Clinician applies it with the probability score; see the age table below |
| 500 to 999 when the doctor's checklist allows a 1,000 cut-off | 500 to 999 ng/mL FEU | 0.5 to 0.99 mg/L FEU | Can still rule out PE when no YEARS item is present 2 or clinical probability is low under PEGeD 6 | Clinician applies the rule; imaging if a YEARS item is present |
| Above every rule-out cut-off | Over 1,000 ng/mL FEU, or over 500 when a YEARS item is present or probability is moderate | Over 1.0 mg/L FEU (or over 0.5 in those cases) | Clot possible; also infection, surgery, pregnancy, cancer, DIC 14 | Leg ultrasound or CT pulmonary angiography if a clot is suspected 2 |
Your age-adjusted cut-off
From age 50, D-dimer drifts up with age, and a fixed 500 line flags most older people. The ADJUST-PE study used age x 10 ng/mL FEU instead, in people whose doctor had not judged PE likely. Of those with a D-dimer between 500 and their age-adjusted cut-off who were left untreated, 1 in 331 (0.3%) had a clot over the next 3 months 3. In other words, the age-adjusted line let more older people safely skip a scan.
| Age | Age-adjusted cut-off (ng/mL FEU) | Same in mg/L FEU |
|---|---|---|
| Under 50 | 500 | 0.50 |
| 55 | 550 | 0.55 |
| 60 | 600 | 0.60 |
| 65 | 650 | 0.65 |
| 70 | 700 | 0.70 |
| 72 | 720 | 0.72 |
| 75 | 750 | 0.75 |
| 80 | 800 | 0.80 |
| 90 | 900 | 0.90 |
The age-adjusted cut-off was tested for suspected PE 3; whether your lab or clinician also applies it to a suspected DVT varies. A low D-dimer is rarely a concern; see the main <a href="/biomarkers/d-dimer">D-dimer page</a>.
When it is urgent
No laboratory critical value exists for D-dimer, because the number alone does not separate a dangerous clot from a recent operation; urgency comes from symptoms and the clinician's judgement of probability 2. A very high D-dimer in someone who is already unwell with fever, bleeding or bruising, or low platelets also needs same-day care, because that pattern can mean DIC 1. A fast heartbeat on its own has many causes, sorted on the <a href="/symptoms/heart-palpitations">palpitations page</a>, and feeling faint without these other signs is covered on the <a href="/symptoms/dizziness">dizziness page</a>.
Other reasons it reads high
Before reading a high D-dimer as a clot, check the common things that push it up:
- Age over 50: D-dimer rises with age, and before age adjustment only about 1 in 16 people aged 75 or older got a normal result, against about 3 in 10 with the age-adjusted cut-off 3.
- Pregnancy and the weeks after birth: D-dimer climbs each trimester, and most women are above 500 ng/mL FEU by the third trimester 1. Hormonal contraception has its own effects on clotting tests, covered in <a href="/learn/birth-control-and-blood-tests">birth control and blood tests</a>.
- Recent surgery, injury, a fracture or a large bruise: clot breakdown at the wound raises D-dimer for days to weeks 4.
- A recent infection or inflammatory flare: raises D-dimer, which falls as the illness settles 1.
- A hospital stay: inpatients have a raised D-dimer so often that a normal-result rule-out rarely works for them, and guidelines lean on imaging instead 4.
- Units or assay: a DDU number read against an FEU cut-off, or a result compared across two labs, can look high or normal by a factor of 2 1.
Strenuous exercise and a difficult blood draw can also nudge the result 1. Once made, D-dimer is cleared within about a day (its half-life is roughly 8 hours), so levels fall once the trigger settles, and a repeat test a few weeks after an infection or operation often reads lower 1. A retest is the clinician's call, and with symptoms no one should wait for one; for how to read two results side by side, see <a href="/learn/trends-beat-single-readings">why trends beat single readings</a>.
Causes
Common
| Cause | Why it raises D-dimer | The clue | What confirms it |
|---|---|---|---|
| Age over 50 | More background clot turnover | Number sits between 500 and age x 10 | Age-adjusted cut-off 3 |
| Pregnancy and after birth | Clotting factors rise to prepare for birth | Pregnant or recently delivered | History; pregnancy-adapted YEARS rules during pregnancy only 5 |
| Recent surgery or injury | Wound clots dissolving | Operation or trauma in the last few weeks | History; repeat later 4 |
| Infection or inflammation | Inflammation switches on clotting | Fever, high CRP | <a href="/biomarkers/crp/high">CRP</a> 1 |
For the inflammation check, the <a href="/biomarkers/crp/high">high CRP page</a> sets the line: "on a standard CRP test, values above 10 mg/L usually mean active inflammation such as an infection, injury or flare."
Less common
| Cause | Why it raises D-dimer | The clue | What confirms it |
|---|---|---|---|
| Active cancer | Tumors make pro-clotting substances | Weight loss, known cancer | Cancer work-up by your doctor 1 |
| Liver disease | D-dimer is cleared more slowly | Abnormal liver tests | Liver panel (<a href="/learn/liver-enzymes-explained">liver enzymes explained</a>), <a href="/biomarkers/albumin-serum/low">albumin</a> 1 |
| <a href="/conditions/chronic-kidney-disease">Kidney disease</a> | Slower clearance | Raised creatinine | <a href="/biomarkers/creatinine-serum/high">Creatinine</a>, <a href="/learn/kidney-function-explained">kidney function explained</a> 1 |
| Heart failure, atrial fibrillation, recent heart attack | Slow blood flow and heart muscle injury | Breathlessness, irregular pulse | <a href="/biomarkers/bnp/high">BNP</a>, <a href="/biomarkers/troponin-i-hs/high">troponin</a>, <a href="/learn/cardiac-markers-explained">heart markers</a> 1 |
| Sepsis and severe infection, including COVID-19 | Widespread clotting in small vessels | Very unwell, often in hospital | Clinical assessment 1 |
Must not miss
| Cause | Why it raises D-dimer | Red flag | What confirms it |
|---|---|---|---|
| DVT | Clot in a deep leg vein breaking down | One swollen painful calf: same-day care | Leg ultrasound 24 |
| Pulmonary embolism | Clot in the lung arteries | Sudden breathlessness, chest pain on breathing, coughing blood: emergency | CT pulmonary angiography (a CT scan with dye that shows the lung arteries) or V/Q scan (a nuclear scan of airflow and blood flow in the lungs) 2 |
| DIC | Clotting and bleeding across the body at once | Unwell with bleeding or bruising: emergency | <a href="/biomarkers/platelet-count/low">Platelets</a>, <a href="/biomarkers/prothrombin-time">PT</a>, <a href="/biomarkers/fibrinogen">fibrinogen</a> 1 |
Symptoms
A high D-dimer causes no symptoms by itself; it is a fragment in the blood, and any symptoms come from what is producing it. Someone with a D-dimer of 700 ng/mL FEU after a chest infection usually feels nothing from the number. A DVT tends to cause one-sided leg swelling, warmth and pain; a PE tends to cause sudden breathlessness, chest pain and a fast heart rate 2. Tiredness, headaches or general aches are not caused by a raised D-dimer.
Read it with your other markers
Markers that sort the causes of a high D-dimer
| Pattern | What it suggests | Read more |
|---|---|---|
| High D-dimer, normal platelets, PT and fibrinogen | Local clot or a non-clot cause such as age, surgery or infection | <a href="/learn/clotting-tests-explained">Clotting tests explained</a> |
| High D-dimer, low platelets, long PT, low fibrinogen | The pattern scored for DIC 1 | <a href="/biomarkers/platelet-count/low">Low platelets</a> |
| High D-dimer with high CRP or ESR (erythrocyte sedimentation rate, another inflammation test) | Inflammation or infection is a likely contributor | <a href="/learn/inflammation-markers-explained">Inflammation markers</a>, <a href="/biomarkers/esr/high">high ESR</a> |
| High D-dimer with high BNP | Heart strain; PE and heart failure both do this | <a href="/biomarkers/bnp/high">High BNP</a> |
What usually happens next
How a doctor works through a high D-dimer
What can bring it down
D-dimer comes down when its cause settles: the infection clears, the wound heals, the pregnancy ends, or a clot is treated by the medical team 1. None of the guidelines cited here lists a food, diet or supplement as a way to lower D-dimer, and products sold as natural clot dissolvers are no substitute for finding the cause 24. If a clot is found, treatment is a prescribed anticoagulant chosen by the medical team 2. Never start aspirin or another blood thinner on your own because of a D-dimer result.
Free, no accountRead your blood testHave the full report with your D-dimer, platelets and clotting times? Read every marker on it line by line; the file stays on your device.Read my results
Citations
- Favresse J, Lippi G, Roy PM, et al. D-dimer: preanalytical, analytical, postanalytical variables, and clinical applications. Crit Rev Clin Lab Sci. 2018;55(8):548-577.
- Konstantinides SV, Meyer G, Becattini C, et al. 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism. Eur Heart J. 2020;41(4):543-603.
- Righini M, Van Es J, Den Exter PL, et al. Age-adjusted D-dimer cutoff levels to rule out pulmonary embolism: the ADJUST-PE study. JAMA. 2014;311(11):1117-1124.
- Lim W, Le Gal G, Bates SM, et al. American Society of Hematology 2018 guidelines for management of venous thromboembolism: diagnosis of venous thromboembolism. Blood Adv. 2018;2(22):3226-3256.
- van der Pol LM, Tromeur C, Bistervels IM, et al. Pregnancy-adapted YEARS algorithm for diagnosis of suspected pulmonary embolism. N Engl J Med. 2019;380(12):1139-1149.
- Kearon C, de Wit K, Parpia S, et al. Diagnosis of pulmonary embolism with d-dimer adjusted to clinical probability. N Engl J Med. 2019;381(22):2125-2134.
Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.
