Absorption Performance of Menstrual Products Tested with Human Blood: Implications for Heavy Menstrual Bleeding Diagnosis

Study Overview and Motivation

A groundbreaking study published in August 2023 revealed a significant discrepancy between the labeled absorption capacity of menstrual products and their actual performance when tested with human blood. This investigation, recognized as the first to systematically measure the absorption rate of various menstrual products using real human blood, raises important questions for women's health, particularly regarding the diagnostic criteria for Heavy Menstrual Bleeding (HMB).

The research was motivated by a clinical gap. With the increasing patient adoption of reusable products like menstrual cups, existing HMB diagnostic standards—developed based on the use of traditional pads and tampons—proved inadequate. The current benchmark, the Pictorial Blood Loss Assessment Chart (PBAC), diagnoses HMB when total menstrual blood loss exceeds 80 milliliters per cycle. The study posits that this diagnosis relies on unreliable product absorption data.

Methodology: From Saline to Human Blood

The research team, led by clinician and hematology professor Dr. Bethany Samuelson Bannow, conducted controlled laboratory tests using expired human blood from a blood bank. They evaluated 21 products, including sanitary pads, panty liners, tampons, menstrual cups, discs, and period underwear.

The core methodological shift was the fluid medium. Industry standard tests for labeling typically use saline solution, a homogeneous liquid. In contrast, human menstrual blood is a complex mixture of blood cells, proteins, and endometrial tissue, which affects its viscosity and absorption characteristics.

Key Findings: Measured Capacity vs. Labeled Claims

The comparative analysis yielded several technically significant observations:

1. General Overstatement of Labels: Most products tested absorbed less human blood than their labeled capacity indicated, a direct consequence of the saline-based test protocol.

2. Product-Specific Performance Variances:

◦ Period Underwear: Demonstrated a practical absorption range of only 1-3 milliliters. This contrasts sharply with some e-commerce claims for similar products citing up to ~40 mL. The tested models showed minimal practical difference in absorption despite different "flow" labels.

◦ "Light" Tampons & Pads: Pads/liners absorbed 3-4 mL. Tampons labeled for light flow absorbed 20-34 mL of human blood.

◦ "Heavy" or "Super" Pads: Outperformed expectations, with one model absorbing up to 52 mL despite labels indicating 10-20 mL.

◦ Menstrual Cups and Discs: Showed the highest volumetric capacity. One model could hold approximately 80 mL when completely filled, making it a functional option for managing very high flow.

Clinical Implications for HMB Diagnosis

The findings directly challenge the parameters used in clinical assessment. Common diagnostic heuristics, such as diagnosing HMB based on saturation of a pad or tampon within 1-2 hours, may be set at an unrealistically high threshold, leading to underdiagnosis.

For instance, the data suggests that saturating two "super" pads (absorbing ~100 mL) or three "super" tampons (absorbing ~90 mL) in one cycle already indicates blood loss exceeding the 80 mL HMB diagnostic threshold. This reveals a potential flaw in applying product-based saturation cues as a diagnostic proxy.

Context and Industry Significance

This study underscores a broader issue of research neglect in menstrual health. Comparative analysis of medical literature databases shows that annual publications on "erectile dysfunction" have historically outnumbered those on "menstrual blood" by a significant margin. Standardized clinical guidelines for assessing menstrual blood loss were not established until the early 2000s.

The research also highlights the practical challenges of using human blood for testing, including resource scarcity, biosafety requirements, and cost. While synthetic blood is available, it is cost-prohibitive for routine testing. The authors note limitations, such as differences between banked blood and actual menstrual fluid, and the controlled pour method versus natural flow.

Conclusion and Direction

This study provides parameterized evidence that the assumed absorption performance of menstrual products is inconsistent with their function under biologically relevant conditions. It calls for a critical review of the clinical guidelines for HMB diagnosis, advocating for standards informed by more physiologically accurate data. Ultimately, it advances the technical discussion needed to improve diagnostic accuracy and product labeling, moving toward better, data-driven health outcomes.