In plain English
UK memory clinics now record dementia diagnoses using ICD-11, the World Health Organization's 2022 classification. This page lists every code you are likely to see on an assessment letter, what each means in everyday terms, and what it implies for treatment.
Why codes appear in the letter
Memory clinics, including The Dementia Service and most NHS services, code each diagnosis using ICD-11. The codes are universal across the UK and internationally, which means they survive referrals, second opinions and moves between regions. They also encode information about the type of dementia, severity, and any modifier such as behavioural symptoms.
A typical line reads:
"ICD-11 6D80.2 — Alzheimer's Disease Dementia, Mixed Type, with Cerebrovascular Disease, mild in degree, with 6D86.4 agitation."
That single line tells the next clinician: the underlying disease (Alzheimer's), the vascular contribution, the severity (mild), and the prominent behavioural symptom (agitation).
The code list
Delirium and MCI
- 6D70 Delirium: acute confusional state, almost always caused by an underlying medical problem (infection, pain, dehydration, medication, substance withdrawal). Distinct from dementia.
- 6D71 Mild Neurocognitive Disorder (also called MCI): measurable cognitive change without significant interference with daily independence. About a quarter progress to dementia within five years.
- 6D72 Amnestic Disorder: prominent memory impairment with relative preservation of other domains.
Dementia due to Alzheimer's Disease (6D80 family)
- 6D80 Dementia due to Alzheimer's Disease (parent code).
- 6D80.0 with Early Onset (before age 65).
- 6D80.1 with Late Onset (from age 65).
- 6D80.2 Mixed Alzheimer's Disease Dementia with Cerebrovascular Disease (the most common pattern in older adults).
- 6D80.3 Mixed Alzheimer's Disease Dementia with other non-vascular aetiologies.
- 6D80.Z Onset unknown or unspecified.
Other dementia categories
- 6D81 Dementia due to Cerebrovascular Disease (Vascular Dementia).
- 6D82 Dementia due to Lewy Body Disease.
- 6D83 Frontotemporal Dementia (including Primary Progressive Aphasia variants).
- 6D84 Dementia due to psychoactive substances (alcohol, sedatives, volatile inhalants).
- 6D85 Dementia due to diseases classified elsewhere (including Parkinson's, Huntington's, NPH, head injury, HIV, prion disease, Down syndrome).
- 6D85.0 Parkinson's Disease Dementia.
- 6D85.6 Normal Pressure Hydrocephalus.
Behavioural and psychological symptoms in dementia (6D86 family)
- 6D86.0 Psychotic symptoms.
- 6D86.1 Mood symptoms.
- 6D86.2 Anxiety symptoms.
- 6D86.3 Apathy.
- 6D86.4 Agitation or aggression.
- 6D86.5 Disinhibition.
- 6D86.6 Wandering.
These modifier codes are added alongside the main diagnosis where relevant.
Severity descriptors
Severity is described as mild, moderate or severe. The threshold between Mild Neurocognitive Disorder and Dementia is functional, not radiological: dementia requires impairment severe enough to interfere with independent activities of daily living.
What the code changes in practice
Different codes change treatment in concrete ways:
- 6D80 family: Cholinesterase Inhibitors and Memantine are licensed.
- 6D81: Cholinesterase Inhibitors not licensed; aggressive vascular risk reduction is core.
- 6D82: Cholinesterase Inhibitors often very helpful; antipsychotics contraindicated.
- 6D83: Cholinesterase Inhibitors not recommended; symptomatic SSRI use for behavioural symptoms.
- 6D71 (MCI): anti-dementia medication not indicated; focus on reversible contributors, lifestyle, and follow-up.
The code also informs prognosis and the framework for benefits and services applications.
Frequently asked questions
Why does my letter use a number rather than a name?
ICD-11 codes are universal and unambiguous, which makes referrals and records portable. The name (e.g. 'Alzheimer's Disease') usually appears alongside the code.
Are ICD-11 codes used internationally?
Yes. ICD-11 is the World Health Organization's classification, used worldwide. The codes mean the same in every country that has adopted ICD-11.
What is the difference between ICD-11 and DSM-5?
DSM-5 is the American Psychiatric Association's diagnostic manual. ICD-11 is the WHO's international classification. The two largely overlap but use different terminology: 'Neurocognitive Disorder' in DSM-5 corresponds to 'Dementia' or 'Mild NCD' in ICD-11.
Can my code change over time?
Yes. Severity can change as the disease progresses. The underlying type usually does not change, but the formulation may be refined as new features emerge.
How is mild, moderate or severe decided?
By how much the cognitive impairment interferes with daily independence, not by imaging or cognitive score alone.
References
- World Health Organization. ICD-11 for Mortality and Morbidity Statistics. 2026 release.
- NICE NG97: Dementia, assessment, management and support.
- Sachdev PS et al. Classifying neurocognitive disorders: the DSM-5 approach. Nat Rev Neurol 2014.
- Alzheimer's Society. Glossary of diagnostic terms.