HERDOO2 Score Calculator

Estimate recurrent VTE risk category in women after first unprovoked venous thromboembolism using the HERDOO2 clinical rule.

Last updated on: June 14, 2026

Calculate HERDOO2 Score

HERDOO2 was validated to identify low-risk women. It does not identify a low-risk subgroup among men.
Use the intended setting only when assessing anticoagulation discontinuation after a first unprovoked VTE and completion of short-term treatment.
Select Yes if any of the following is present in either leg: hyperpigmentation, edema, or redness.
Enter D-dimer value. The original HERDOO2 criterion uses D-dimer ≥250 µg/L while the patient is receiving anticoagulation. Use assay-specific judgment when your lab reports different calibration systems.
The original HERDOO2 rule used D-dimer measured during anticoagulant treatment.
kg/m²
Obesity criterion is positive when BMI is 30 kg/m² or higher.
years
Older age criterion is positive when age is 65 years or higher.

What is the HERDOO2 score?

The HERDOO2 score is a clinical decision rule used to help identify women at low risk of recurrent venous thromboembolism after a first unprovoked VTE.

It was developed to support decisions about whether anticoagulation can be discontinued after completing short-term treatment, but the decision must also consider bleeding risk, recurrence risk and patient preference.

HERDOO2 score formula

The HERDOO2 formula assigns 1 point for each positive criterion: hyperpigmentation, edema or redness in either leg; D-dimer ≥250 µg/L while on anticoagulation; BMI ≥30 kg/m²; and age ≥65 years.

Women with a score of 0 or 1 are considered low risk in the intended population. Women with 2 or more criteria and all men are not classified as low risk by this rule.

HERDOO2 score interpretation

Low recurrent VTE risk by HERDOO2: Score 0–1 in the intended female population. Anticoagulation discontinuation may be discussed after short-term treatment, provided the full clinical context supports it.
High recurrent VTE risk by HERDOO2: Score ≥2 in a woman. The HERDOO2 rule does not support classifying this patient as low risk; extended anticoagulation is often considered if bleeding risk is acceptable.
Not low risk by HERDOO2 rule: HERDOO2 was not validated to identify low-risk men. Men with unprovoked VTE are generally not classified as low risk using this rule.
Outside intended HERDOO2 population: The score is displayed, but the patient setting is outside or uncertain for the original validated use. Do not use the result alone to stop anticoagulation.

Required inputs

  • Patient sex, because HERDOO2 is intended to identify low-risk women.
  • Clinical setting: first unprovoked VTE after completion of short-term anticoagulation.
  • Presence of hyperpigmentation, edema or redness in either leg.
  • D-dimer value, ideally measured while the patient is receiving anticoagulation, using an assay-appropriate cut-off.
  • BMI and age, using cutoffs of BMI ≥30 kg/m² and age ≥65 years.

Important limitations

HERDOO2 is a decision-support rule and should not be used as an automatic instruction to stop anticoagulation.

  • It is intended for women with a first unprovoked VTE after completing short-term anticoagulation.
  • It does not identify a low-risk subgroup among men.
  • The D-dimer cut-off is assay-specific; the original rule used a 250 µg/L threshold while on anticoagulation.
  • It should not be applied to clearly provoked VTE, active cancer-associated thrombosis or situations requiring anticoagulation for another reason.
  • Final anticoagulation duration should consider bleeding risk, patient preference, recurrence risk factors and current clinical guidelines.

This page has been medically reviewed by Dr. Khoulah Attia – PharmD, Immunology Specialist.

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