The Katz Index and What Its Six Items Really Measure

What does the Katz Index actually measure?

The Katz Index rates six basic self-care functions and nothing else: bathing, dressing, going to the toilet, transferring in and out of a bed or chair, continence, and feeding. Each one gets a single binary judgment - independent, or dependent - with no partial credit and no half marks 1Ref 1Katz S, Ford AB, Moskowitz RW, Jackson BA, Jaffe MW. (1963).Studies of Illness in the Aged: The Index of ADL: A Standardized Measure of Biological and Psychosocial Function.The six items of the Katz Index (bathing, dressing, going to toilet, transferring, continence, feeding); the binary independent/dependent rating; the ordered A-G letter grading and its direction from most to least independent, including the 'Other' category; the original development sample of more than 2,000 assessments across 1,001 elderly and chronically ill individuals; and the absence in this paper of any cutoff, minimal important change, or measurement-error figure.. Six yes-or-no answers is the entire instrument, which is why it takes minutes rather than an afternoon.

Sidney Katz and colleagues published it in 1963 as a standardized measure of biological and psychosocial function rather than a diagnosis, drawing on more than 2,000 assessments of 1,001 older and chronically ill people 1Ref 1Katz S, Ford AB, Moskowitz RW, Jackson BA, Jaffe MW. (1963).Studies of Illness in the Aged: The Index of ADL: A Standardized Measure of Biological and Psychosocial Function.The six items of the Katz Index (bathing, dressing, going to toilet, transferring, continence, feeding); the binary independent/dependent rating; the ordered A-G letter grading and its direction from most to least independent, including the 'Other' category; the original development sample of more than 2,000 assessments across 1,001 elderly and chronically ill individuals; and the absence in this paper of any cutoff, minimal important change, or measurement-error figure.. The six domains are what clinicians mean when they say basic activities of daily living: the work of keeping a body clean, clothed, fed, and moved from one place to another.

What the Index leaves out matters as much as what it includes. There is no item for cooking, money, driving, or memory. A person can be rated fully independent on all six and still be unable to run a household.

The six items, in the order Katz wrote them

Each item asks one question: does this person do it without help from another person? Hands-on assistance, standby supervision, and prompting all count as help. The 1963 wording is a little old-fashioned, and current health-system lists phrase two of the items differently, which is a reliable source of confusion when two documents describe the same person.

The original six are bathing, dressing, going to toilet, transferring, continence, and feeding 1Ref 1Katz S, Ford AB, Moskowitz RW, Jackson BA, Jaffe MW. (1963).Studies of Illness in the Aged: The Index of ADL: A Standardized Measure of Biological and Psychosocial Function.The six items of the Katz Index (bathing, dressing, going to toilet, transferring, continence, feeding); the binary independent/dependent rating; the ordered A-G letter grading and its direction from most to least independent, including the 'Other' category; the original development sample of more than 2,000 assessments across 1,001 elderly and chronically ill individuals; and the absence in this paper of any cutoff, minimal important change, or measurement-error figure.. The modern phrasing of the same domains - bathing, dressing, eating, toileting, transferring, continence - is what most health systems now publish 2Ref 2Cleveland Clinic (2023).Activities of Daily Living (ADLs and IADLs).The current phrasing of the basic ADL domains (bathing, dressing, eating, toileting, transferring, continence) and the distinction between basic ADLs and instrumental ADLs such as meal preparation, medication, shopping, and managing money, used to assess how much help a person needs.. The vocabulary changed; the six domains did not. "Feeding" and "eating" are the same item.

How the Katz is scored: letters, not points

The original Katz Index does not produce a number. It produces an ordered letter grade from A to G that runs from most independent to most dependent: A means independent in all six functions, G means dependent in all six, and an "Other" category exists for people whose pattern of dependency does not fit the hierarchy in between 1Ref 1Katz S, Ford AB, Moskowitz RW, Jackson BA, Jaffe MW. (1963).Studies of Illness in the Aged: The Index of ADL: A Standardized Measure of Biological and Psychosocial Function.The six items of the Katz Index (bathing, dressing, going to toilet, transferring, continence, feeding); the binary independent/dependent rating; the ordered A-G letter grading and its direction from most to least independent, including the 'Other' category; the original development sample of more than 2,000 assessments across 1,001 elderly and chronically ill individuals; and the absence in this paper of any cutoff, minimal important change, or measurement-error figure.. Further down the alphabet means more help needed.

The version most families actually meet is a different animal. Somewhere downstream of 1963, the same six items were re-expressed as a summed 0-6 point score in which 6 means independent in all six and 0 means dependent in all six. That reverses the direction of travel: on the letters, later is worse; on the points, lower is worse. The 1963 paper describes the letters 1Ref 1Katz S, Ford AB, Moskowitz RW, Jackson BA, Jaffe MW. (1963).Studies of Illness in the Aged: The Index of ADL: A Standardized Measure of Biological and Psychosocial Function.The six items of the Katz Index (bathing, dressing, going to toilet, transferring, continence, feeding); the binary independent/dependent rating; the ordered A-G letter grading and its direction from most to least independent, including the 'Other' category; the original development sample of more than 2,000 assessments across 1,001 elderly and chronically ill individuals; and the absence in this paper of any cutoff, minimal important change, or measurement-error figure.; the point score is a later adaptation of its items, and attributing that scale to Katz is one of the most common errors in circulation.

Before reacting to a Katz result, ask which version produced it. "A 6" and "a G" describe opposite people.

What a Katz score cannot tell you

A Katz result is a description, not a threshold. The 1963 paper sets no cutoff at which a person is declared to need care, and it publishes no figure for how much change on the scale counts as real or as meaningful 1Ref 1Katz S, Ford AB, Moskowitz RW, Jackson BA, Jaffe MW. (1963).Studies of Illness in the Aged: The Index of ADL: A Standardized Measure of Biological and Psychosocial Function.The six items of the Katz Index (bathing, dressing, going to toilet, transferring, continence, feeding); the binary independent/dependent rating; the ordered A-G letter grading and its direction from most to least independent, including the 'Other' category; the original development sample of more than 2,000 assessments across 1,001 elderly and chronically ill individuals; and the absence in this paper of any cutoff, minimal important change, or measurement-error figure.. Someone who moves one step has not crossed a validated line; an assessor has described them differently, which may or may not reflect a genuine shift.

Three further limits are worth holding onto.

The binary hides the middle. Independent or dependent is the only choice available, so a man who showers alone and a man who showers with someone standing outside the curtain in case he slips can land on opposite sides of a line that describes neither well. Most real decline happens in that middle.

It ignores the instrumental half of life. Cooking, shopping, medication, transport, and money are instrumental activities - a separate category from basic self-care, and the reason the difference between ADLs and IADLs comes up in nearly every care conversation 2Ref 2Cleveland Clinic (2023).Activities of Daily Living (ADLs and IADLs).The current phrasing of the basic ADL domains (bathing, dressing, eating, toileting, transferring, continence) and the distinction between basic ADLs and instrumental ADLs such as meal preparation, medication, shopping, and managing money, used to assess how much help a person needs.. The Lawton IADL Scale was built for that half, which a Katz result leaves unmeasured.

It says nothing about why. The six items record what a person does, not whether the cause is arthritis, a stroke, pain, low mood, fear of falling, or a medication that makes standing up feel dangerous. Only a clinical evaluation answers that, and the answer is what determines whether any of it is reversible.

Where an ADL count decides what gets paid for

The number of dependent items on a Katz-style assessment is not just clinical shorthand. It is the switch several public programs use to decide what they will fund, and they do not all use it the same way - which is why one assessment can qualify a person for one benefit and not another.

Medicare. The home health benefit covers part-time or intermittent skilled care - skilled nursing and physical, occupational, or speech therapy - plus a part-time home health aide, but only alongside that skilled care. It explicitly does not pay for 24-hour-a-day care at home, delivered meals, or custodial and personal care when that is the only care needed 3Ref 3Centers for Medicare & Medicaid Services (2025).Home Health Services Coverage.What Original Medicare's home health benefit covers - part-time or intermittent skilled nursing and therapy, with a home health aide only alongside skilled care - and its explicit exclusions of 24-hour-a-day care at home, delivered meals, and custodial or personal care when that is the only care needed.. A high count of dependent ADLs does not, on its own, open this door.

Medicaid. Community First Choice, the Section 1915(k) state plan option, pays for attendant services covering ADL, IADL, and health-related tasks. States adopting it must serve everyone meeting an institutional level of care, cannot cap enrollment, and receive a six-percentage-point increase in federal match 4Ref 4Centers for Medicare & Medicaid Services (2025).Community First Choice (CFC) 1915(k).Section 1915(k) Community First Choice as a state plan option covering attendant services for ADL, IADL, and health-related tasks; the requirement that participating states serve people meeting an institutional level of care and not cap enrollment; and the six-percentage-point FMAP increase states receive for adopting it.. That level-of-care finding is the determination a functional assessment feeds.

VA. The Homemaker and Home Health Aide program provides personal care and ADL assistance in a veteran's own home under registered-nurse supervision, offered as an alternative to nursing home care and as respite for a family caregiver; a copay may apply depending on service-connected status 5Ref 5U.S. Department of Veterans Affairs (2024).Homemaker and Home Health Aide Care - Geriatrics and Extended Care.The VA Homemaker and Home Health Aide program providing personal-care and ADL assistance in a veteran's home under registered-nurse supervision, as an alternative to nursing home care and for caregiver respite, with a possible copay depending on service-connected status..

If a private long-term care insurance policy is in play, its own definitions section is the authority - the activities it counts are not always the Katz six, and the exact paragraph is worth asking for.

What actually happens during an assessment

An assessment is usually a conversation with some watching folded into it. A nurse, social worker, occupational or physical therapist, or a case manager asks how each of the six goes on an ordinary day, and often asks to see one or two of them - standing up out of a chair, walking as far as the bathroom door. The result depends heavily on how the questions get answered.

The most common distortion is the good-day answer. Asked "can you dress yourself?", a proud person says yes, because on a good morning they can. The thing the score is meant to capture is closer to "on how many mornings this week did somebody help?" An adl and iadl checklist filled in across seven real days does more for the accuracy of the result than anything said in the room. The score should describe an ordinary week, not the best morning in it.

It also helps to separate what a person can do from what they actually do. Someone physically able to bathe who has not bathed in two weeks is not independent in any way that matters, and that gap belongs in the conversation even though the instrument has no box for it.

Turning six letters into an actual care plan

The point of the exercise is hours: how many, at what times of day, doing what. Someone dependent only in bathing and dressing generally needs a person present at the two ends of the day. Add transferring, toileting, and continence, particularly overnight, and the arithmetic changes shape - the conversation moves toward overnight coverage or a live-in arrangement, and what a live-in caregiver really costs becomes the next question a family has to answer.

Some scale is worth having before that conversation. About 60% of people will need some long-term care help at some point, most of it delivered at home by unpaid family members and typically lasting one to two years; roughly 20% of today's 65-year-olds will need help for longer than five years, and about 20% may never need it at all 6Ref 6Administration for Community Living (2025).How Much Care Will You Need?.Federal long-term-care planning statistics: about 60% of people will need some long-term care help; most care is provided at home by unpaid caregivers and typically lasts one to two years; and among today's 65-year-olds roughly 20% will need help longer than five years while about 20% may never need it.. Needing help with some of the six is not the beginning of the end of living at home. For many families it turns out to be a chapter rather than a permanent state.

The six letters decide nothing on their own. What they do is give a family, a clinician, and a payer the same vocabulary for a single question - how much help, with what - so the argument can be about the plan instead of about the facts.