A young adult in rural Bangladesh receives a diabetes diagnosis, but the textbook treatment plan makes no sense. They are not overweight. They show no signs of the autoimmune attack that defines type 1 diabetes. Metformin, the standard first-line drug for type 2, barely moves their blood sugar. Across clinics in sub-Saharan Africa and South Asia, doctors have encountered this same confounding profile for decades. Now, a growing body of peer-reviewed research is giving it a name and a framework: malnutrition-related diabetes mellitus, or MRDM, sometimes called “type 5” diabetes.
A 2022 study published in Diabetes Care, led by researchers including Emory University’s K.M. Venkat Narayan, examined patients in low- and middle-income countries who developed diabetes despite having a very low body mass index. The team documented distinct patterns of insulin secretion and insulin sensitivity that did not match type 1 or type 2 diabetes. These patients lacked the autoimmune markers that characterize type 1, yet they had severe deficits in insulin production that oral medications alone could not correct. The findings pointed to a unique form of beta-cell dysfunction rooted not in immune destruction or obesity, but in chronic undernutrition.
A diagnosis that keeps falling through the cracks
The concept is not new. The World Health Organization included MRDM in its diabetes classification in 1985, only to remove it in 1999, citing insufficient evidence at the time. For the next two decades, patients who fit this profile were often shoehorned into type 1 or type 2 categories, receiving treatments designed for fundamentally different metabolic problems.
What has changed is the quality of evidence. The Diabetes Care study and related research have used standardized protocols for measuring insulin secretion, careful exclusion of autoimmune markers, and direct comparison against established diabetes categories. A related analysis traced the clinical phenotype across geographic cohorts in sub-Saharan Africa and South Asia, regions where food insecurity and diabetes increasingly overlap. The consistency of findings across countries argues against a local anomaly and supports a shared pathway driven by early-life nutritional deprivation.
A clinician-facing review published on the NCBI Bookshelf through the Endotext platform now places MRDM within a broader differential diagnosis of lean diabetes in tropical settings. That review separates MRDM from fibrocalcific pancreatic diabetes, ketosis-prone diabetes, and maturity-onset diabetes of the young (MODY), each of which can also appear in lean adults in the tropics. The distinction matters because each subtype responds differently to treatment. Patients with fibrocalcific pancreatic diabetes, for instance, have visible pancreatic calcifications on imaging and often present with chronic abdominal pain. MRDM patients frequently show no such structural damage but still require insulin therapy combined with nutritional rehabilitation.
What sets MRDM apart at the bedside
Clinical descriptions across the research literature highlight a recurring profile. Affected individuals tend to be diagnosed in adolescence or early adulthood, often with a history of childhood stunting or repeated food shortages. They present with marked hyperglycemia but are usually not in diabetic ketoacidosis, which distinguishes them from classic new-onset type 1 cases. Many can survive without insulin for stretches of time, yet they fail to achieve adequate blood sugar control on standard oral regimens alone.
When insulin is introduced in carefully titrated doses, glycemic control improves, but weight gain remains difficult unless nutritional support is provided at the same time. These patterns reinforce the idea that both endocrine and exocrine pancreatic function have been compromised by years of undernutrition, not by autoimmune destruction or excess caloric intake. In practical terms, a treatment plan built around weight reduction and metformin could be ineffective or even harmful for someone whose pancreas was damaged by chronic hunger.
Major gaps remain before official recognition
As of May 2026, no major international body, including the WHO or the American Diabetes Association, has formally added “type 5” or MRDM to its official classification system. The current push to reinstate a distinct category rests on peer-reviewed clinical studies and expert reviews rather than on any official reclassification announcement. Whether these findings will prompt a formal update to global diagnostic guidelines depends on larger epidemiological validation, consensus-building within professional societies, and evidence that a separate label will improve patient outcomes compared with refining existing categories.
Large-scale population data from official health registries in affected countries remain scarce. The existing evidence draws primarily from clinical case series, hospital-based cohorts, and small regional surveys rather than from nationally representative samples. This gap makes it difficult to estimate how many people worldwide live with MRDM as opposed to a misdiagnosed form of type 1 or type 2 diabetes. Without reliable numbers, health ministries and international donors lack the data they need to allocate funding for targeted screening and treatment programs.
There are also practical barriers. Diagnosing MRDM with confidence requires C-peptide assays, autoantibody testing, and sometimes high-quality imaging. Clinics in rural India, Nigeria, or Bangladesh often lack access to these tools. Even if formal criteria were agreed upon, resource constraints could force clinicians to rely on simplified algorithms based on age at onset, BMI, history of malnutrition, and response to initial therapy. Those shortcuts may blur the boundaries between MRDM and other atypical diabetes forms.
The long-term natural history of MRDM is another open question. Existing studies provide cross-sectional snapshots or relatively short follow-up periods. It is not yet clear how rapidly complications such as retinopathy, nephropathy, or neuropathy develop in this group compared with type 1 or type 2 patients, or whether aggressive early nutritional rehabilitation can partially restore beta-cell function.
What patients and clinicians can do now
Until global classifications catch up, awareness is the most practical tool for narrowing the treatment gap. Anyone who is lean, lives in a setting where childhood or chronic malnutrition is common, and receives a diabetes diagnosis should ask their clinician whether autoimmune markers and C-peptide levels have been tested. Early consideration of insulin therapy, careful monitoring for hypoglycemia in the context of low body reserves, and structured nutritional support may offer a better path to stable blood sugar control than a standard type 2 protocol.
For the research community, the priority is clear: larger, longer studies that follow MRDM patients over years, track complication rates, and test whether early intervention changes outcomes. The clinical profile has been documented. The mechanistic basis is taking shape. What remains is the hard, slow work of turning that evidence into guidelines, funding, and on-the-ground care for millions of people whose diabetes does not fit the categories the world has built.
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*This article was researched with the help of AI, with human editors creating the final content.
