Category · F70-F79 block
F71 — Moderate mental retardation
Terminology note: ICD-10's own term for this block is "mental retardation." Modern clinical and educational usage prefers "intellectual disability" (used in DSM-5 and in ordinary clinical practice since the mid-2010s), and ICD-11 has renamed and relocated this entire classification territory to "disorders of intellectual development." This page keeps ICD-10's actual code and official title for classification accuracy, and uses person-first language throughout ("a person with an intellectual disability"), never a label standing in for the person.
What is this category?
F71 sits one severity grade below F70 on the same dual-criteria scale — the teaching challenge here is applying the same two-criteria test (intellectual functioning plus adaptive functioning) at a lower approximate IQ range, where support needs are typically more pervasive across daily life.
Core diagnostic concept
F71 requires the same dual criteria as F70 — significantly subnormal intellectual functioning and a matching adaptive-functioning deficit, with developmental onset — at an approximate IQ range of 35-49. Adaptive-functioning needs are typically more pervasive than in mild intellectual disability, commonly including support needs in most areas of daily living, though many people with moderate intellectual disability still develop functional communication and can participate meaningfully in supervised community and work settings.
Key diagnostic features
- Approximate IQ range 35-49
- A lower approximate range than F70, on the same testing basis.
- More pervasive adaptive-functioning support needs
- Support needs typically extend across most areas of daily living, though the degree varies considerably between individuals.
- Functional communication is common
- Many people with moderate intellectual disability develop functional, if simpler, communication skills.
- Onset during the developmental period
- Present from childhood, as with every grade in this block.
How to weigh evidence
These learning labels are teaching aids, not official ICD-10 terminology (see Sources and Method).
- supports Testing in the approximate moderate range together with support needs across most daily-living domains, present since early childhood.
- consistent not decisive A single test score in the moderate range, without any description of adaptive functioning.
- raises alternative Adaptive-functioning needs that are actually milder and more circumscribed than the IQ range alone would suggest — worth checking against F70 rather than assuming F71 from the score alone.
- contradicts or weakens A previously higher level of independent functioning, with a clear, datable later decline.
- missing and necessary to ask How pervasive the adaptive-functioning support needs actually are across different daily-living domains, not just the test score.
Diagnostic boundary
F71 is distinguished from F70 by both a lower approximate IQ range and more pervasive adaptive-functioning support needs, and from F72 by the same dual criteria one grade further along — never by the IQ range alone in either direction.
Full comparisons:
Duration and course
Minimum duration: Onset during the developmental period, as with every grade in this block.
Course: A stable pattern rather than a discrete episode; functional communication and participation in supervised settings often develop with appropriate support.
Included presentations
- Testing in the approximate moderate range together with adaptive-functioning support needs across most daily-living domains, present since childhood.
Exclusions and distinguishing presentations
| If this is true instead… | Consider | Why |
|---|---|---|
| Adaptive-functioning needs and intellectual testing more consistent with the mild range | F70 | The dual criteria, not the IQ range in isolation, decide the grade — a milder adaptive-functioning picture should be checked against F70. |
| Support needs and intellectual functioning more consistent with the severe range | F72 | The same dual criteria, applied at the next threshold, may instead support F72. |
Four-character subtypes (orientation)
As with every category in this block, the fourth character records behavioural impairment independently of the severity grade itself.
- F71.0 — No, or minimal, impairment of behaviour
- Behaviour does not require particular attention or treatment beyond the intellectual disability itself. (in_depth)
- F71.1 — Significant impairment of behaviour, requiring attention or treatment
- A behavioural disturbance (e.g. aggression, self-injury) significant enough to need its own dedicated attention, independent of the intellectual disability grade itself. (in_depth)
- F71.8 — Other impairments of behaviour
- A behavioural picture not fitting the other listed states. (taught for orientation only, not separately assessed in this pilot)
- F71.9 — Without mention of impairment of behaviour
- No information given about whether a behavioural impairment is present. (taught for orientation only, not separately assessed in this pilot)
External causes to check first
Categories in this block require that the disturbance is not better explained by another external cause listed below. These short capsules are reminders, not full teaching modules.
Boundary capsule — The dual criteria and grading logic across F70-F79
A shared reasoning check for every category in this block: none of F70-F73 can be supported by an IQ score alone, none of them can be supported by an adaptive-functioning impression alone, and the severity grade (F70-F73) is a separate question from both the behavioural-impairment fourth character and from whether enough information exists to grade at all (F78 versus F79).
What to check:
- Both criteria, together: is there evidence of both significantly subnormal general intellectual functioning (an approximate IQ range) AND a matching concurrent deficit in adaptive functioning (communication, self-care, home living, social and community skills)? Either one alone, without the other, does not support an F70-F73 classification.
- Onset: has the pattern been present since the developmental period (conventionally, before adulthood), rather than appearing as a decline from a previously typical baseline later in life? A later, datable decline points toward an acquired dementia (F00-F03), not toward this block, however similar the resulting scores look.
- Severity grade versus behavioural-impairment axis: is the question 'how subnormal is intellectual and adaptive functioning' (F70 mild, F71 moderate, F72 severe, F73 profound) being kept separate from the independent fourth-character question 'is there also a significant behavioural impairment requiring its own attention or treatment' (.0-.9)? A significant behavioural impairment does not, by itself, make the severity grade any more or less severe.
- F78 versus F79: when a case cannot be graded into F70-F73, is that because grading is specifically confounded by an identifiable associated sensory, physical, or behavioural impairment that makes standard assessment difficult (points toward F78), or because there is genuinely insufficient information available to grade at all, with no such confound identified (points toward F79)? These are two different reasons for not grading, not interchangeable labels for 'unclear.'
A full standardized cognitive and adaptive-functioning assessment by a qualified professional, which is outside this capsule's scope and is needed before any of these classifications is used in real clinical, educational, or support-planning practice.
Common learner errors
Worked example — placing a presentation at the moderate grade
A 10-year-old communicates in short phrases, needs consistent daily support with dressing, meals, and personal safety, and has needed a substantially adapted curriculum since starting school. Testing places his general intellectual functioning in the approximate moderate range, and this pattern has been consistent since early childhood.
- Step 1 — Check the intellectual-functioning evidence: testing places him in the approximate moderate range (IQ 35-49).
- Step 2 — Check the adaptive-functioning picture: support needs span communication, self-care, and safety — more pervasive than a mild-range picture would typically show.
- Step 3 — Check onset: consistent since early childhood.
- Conclusion — The dual criteria, at this range and this breadth of support need, together support F71 rather than F70 or F72.
Interactive practice
- Type A Needing daily support with new tasks Recognition / application · Foundation
- Type B A serious behavioural problem — does it change the grade? Boundary discrimination · Transfer
Retrieval prompts
Try answering each of these from memory before revealing where to check. Nothing you think or type here is sent or saved anywhere.
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State the approximate IQ range associated with F71.
Reveal answer location
Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.
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Explain what typically distinguishes F71's adaptive-functioning picture from F70's.
Reveal answer location
Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.
These self-checks are a personal study aid only, visible to you on this page for this visit — they are not stored and do not affect your mastery dimensions.
Rapid revision card
F71: The same dual criteria as F70 (subnormal IQ plus matching adaptive-functioning deficit, developmental onset), at an approximate IQ range of 35-49 with typically more pervasive support needs.
Decisive boundary cues:
- More pervasive daily-living support needs than F70's typical picture -> weighs toward F71.
- A milder, more circumscribed support-need picture -> weighs back toward F70.
- Support needs and IQ range consistent with the next threshold down -> weighs toward F72.
Duration/course: Onset during the developmental period, as a stable pattern.
Nearest alternatives: F70, F72
Common mistake: Assigning a grade from the IQ range alone without checking the breadth of the adaptive-functioning picture.
Retrieval prompt: What would make you reconsider this as F70 instead of F71?
(or use your browser's print function) Open full-page printable revision view →
Related glossary terms
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Adaptive functioning
The practical skills a person uses to meet the everyday demands of independent living — communication, self-care, home living, social skills, use of community resources, self-direction, and similar domains — assessed relative to what is typically expected at a person's age and cultural context. A concurrent deficit in adaptive functioning, alongside subnormal intellectual functioning, is one of the two criteria required for an intellectual disability classification (F70-F73); intellectual functioning alone is never sufficient.
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Intelligence quotient (IQ)
A standardized score summarizing performance on a test of general intellectual functioning, used in this block as one part — never the whole — of the evidence for an intellectual disability classification. The approximate ranges conventionally associated with each severity grade (F70 mild ≈ 50-69, F71 moderate ≈ 35-49, F72 severe ≈ 20-34, F73 profound < 20) are never sufficient on their own without a matching adaptive-functioning deficit.
Source basis
WHO ICD-10 international classification structure and code/title (ICD-10 Browser, 2019 English release).
Original educational synthesis, informed by general published clinical-education understanding of ICD-10 F70-F79; no verbatim CDDG or DCR text is reproduced. See Sources and Method for the full policy.
Last reviewed: 2026-09-17. Full policy: Sources and Method.
Educational resource only. This page and its cases teach ICD-10 classification reasoning using fictional scenarios. It does not diagnose real people and should not be used to assess yourself or anyone else. Intellectual disability is not the person — every person with an intellectual disability deserves the same dignity and respect as anyone else. If you are concerned about a child's development, or about an adult's intellectual or adaptive functioning, please speak with a qualified professional for assessment and support.