Menstrual flow, finally measurable.
Joii combines proprietary evaluation pads, AI image analysis and a mobile app to quantify menstrual flow, advancing objective measurement for clinical research and women's healthcare.
UKCA Class I medical device
Evaluated in NHS primary care
THE PROBLEM
Two measurements that matter. Neither is easy to get.
Heavy menstrual bleeding affects around one in four women and can contribute to iron-deficiency anaemia. Yet measuring menstrual bleeding remains a significant challenge.
Menstrual flow contains blood, tissue and other fluids. Understanding it requires two distinct measurements: total menstrual fluid loss and actual menstrual blood loss. Both remain difficult to measure objectively, whether in everyday life or at scale in clinical research.
Menstrual fluid loss
The total volume of menstrual flow, including blood, tissue and other fluids. It may provide valuable insight into the overall bleeding experience, treatment response and impact on daily life. Yet there is no widely accessible, standardised method for routine quantitative measurement.
Menstrual blood loss
The volume of blood lost during menstruation — an important clinical measure for assessing heavy menstrual bleeding and its relationship with iron deficiency and anaemia. Accurate laboratory methods exist, but they are costly, labour-intensive and difficult to scale.
THE SOLUTION
One scan. Two measurements.
Joii transforms a smartphone image of a used proprietary menstrual pad into quantitative menstrual flow data — without laboratory equipment or pad collection.
Menstrual fluid loss: available now. Joii's UKCA-marked, MHRA-registered Class I medical device estimates fluid volume from pad images and tracks menstrual flow across the cycle.
Menstrual blood loss: in development and validation. We are advancing the technology to estimate actual blood loss, using alkaline haematin — the laboratory reference method — to develop and independently validate the next generation of our AI models.
Our goal is to make both measurements available through a single scan.
THE TECHNOLOGY
Measurement science, built into everyday products.
The proprietary pad. Joii's purpose-designed evaluation pad is made to be scanned: one photo, with no extra equipment, gives a consistent measurement from pad to pad.
The AI pipeline. Smartphone images are processed using computer vision and deep-learning models to identify the pad, analyse menstrual staining and estimate fluid volume. The technology is being further developed to improve measurement robustness and support additional capabilities, including clot analysis.
The data. Joii has accumulated more than 70,000 menstrual pad images, alongside curated, reference-labelled datasets used for algorithm development and evaluation. In internal held-out testing, our current fluid-volume model achieved a mean absolute error of 0.72 mL per pad against known reference volumes.
The digital platform. The Joii app supports image capture, menstrual flow tracking and quantitative reporting, creating a foundation for longitudinal monitoring and clinical research applications.
Next: blood-loss measurement. Our planned clinical validation programme will pair pad images with alkaline haematin laboratory measurements to develop and evaluate blood-loss estimation independently.
HOW IT WORKS
A measurement in three steps.
THE EVIDENCE
Built to a medical-device standard, backed by evidence.
Registered medical device: Joii is a UKCA-marked, MHRA-registered Class I medical device.
Scientific validation programme: Led by Prof. Bassel Al-Wattar at Anglia Ruskin University, Joii's research programme aims to independently validate menstrual fluid-volume measurement and advance blood-loss estimation through comparison with alkaline haematin, the laboratory reference method.
Real-world study · University of Bradford: In a twelve-month study, women's confidence in estimating their menstrual blood loss increased from under 5% to over 80%. Period health literacy improved by a median of 52%, communication with clinicians by 33%, and symptom screening by 36%.
NHS primary-care evaluation · NIHR i4i: Among participating GPs, 90% agreed Joii improved patients' period health literacy, while 82% believed its scanner could replace existing methods of assessing menstrual volume and clot size. Most indicated they would use Joii in practice if NHS-approved.
FOR PARTNERS AND RESEARCHERS
Objective measurement for clinical research and care.
Joii is used as an objective measurement tool in clinical research and healthcare settings. If you're running a study or clinical service where menstrual blood loss needs to be measured objectively, we'd love to hear from you. We're also establishing head-to-head validation against the alkaline haematin gold standard.