Lewy Body Dementia Explained: Symptoms, Diagnosis, and Why It's Often Missed

This guide covers hallucinations and delusions as part of explaining a specific type of dementia. If you'd rather read about coping with these symptoms day to day first, our guide on psychosis in dementia covers that directly.

Why this one needed its own guide

Dementia isn't one condition, it's a family of them, and Lewy body dementia is genuinely one of the more common types, not a rare exception. It's estimated to affect more than 100,000 people in the UK, and by some estimates it's the second most common form of degenerative dementia after Alzheimer's disease. Despite that, it's easy to find yourself deep into a diagnosis journey without ever having heard the term, because its symptoms so often get mistaken for something else first.

What dementia with Lewy bodies actually is

Lewy bodies are tiny protein deposits that build up inside brain cells. Where they build up affects what symptoms show up: deposits at the base of the brain are closely linked to the movement problems seen in Parkinson's disease, while deposits in the outer layers of the brain are linked to the thinking and perception problems that are the hallmark of dementia with Lewy bodies (DLB).

In DLB, the cognitive changes, problems with thinking, alertness and perception, usually happen first, often a year or more before any movement symptoms appear. That order matters, because it's part of why diagnosis can take a while to land correctly.

How it's different from Alzheimer's

In the early stages, Lewy body dementia is often mistaken for Alzheimer's, since some symptoms genuinely overlap, particularly problems with thinking and perception. But there are real differences worth knowing:

Memory is often less affected, at least early on. Alzheimer's Society notes that day-to-day memory problems do affect people with DLB, but usually much less than in early Alzheimer's, where memory loss tends to be the main, most obvious feature.

Alertness fluctuates, sometimes dramatically. A defining feature of DLB is that a person may seem confused and withdrawn one moment, then alert and engaged shortly after, changing over the course of hours or even minutes. This isn't the same as the sudden, dramatic confusion of delirium (which is usually triggered by an infection or medical event, and is covered in our guide on sudden confusion and UTIs) — with DLB, this kind of fluctuation is simply part of the condition itself, day to day.

Visual hallucinations are common, and often happen early. Seeing things that aren't there, often detailed and specific, like a person, an animal or a pattern of light, is one of the most recognised features of DLB, and can be one of the earliest symptoms rather than something that only appears later on.

Movement is affected in a way it usually isn't in Alzheimer's. Slowness of movement, muscle stiffness, tremors, and a shuffling walk (sometimes called parkinsonism) can appear, alongside or shortly after the cognitive symptoms.

Sleep is often disturbed in a specific way. Many people with DLB experience a condition where they physically act out their dreams during sleep, shouting, kicking or flailing, which can be distressing or even risky for a partner sharing a bed.

Why diagnosis can take time

Because DLB's early symptoms can resemble Alzheimer's, or even look like a psychiatric condition rather than dementia at all, it's commonly misdiagnosed or missed altogether in the early stages. As more symptoms appear together, hallucinations alongside movement changes alongside fluctuating alertness, doctors are usually able to identify it more confidently. If a diagnosis doesn't feel like it fits what you're actually seeing at home, it's entirely reasonable to ask the GP for a referral to a neurologist or dementia specialist for a fuller assessment.

The one medication warning every family needs to know

This is genuinely important, not a minor footnote. Many people with Lewy body dementia are particularly sensitive to a class of medications called antipsychotics, sometimes prescribed for hallucinations or agitation in other forms of dementia. In people with DLB, the wrong antipsychotic can cause a severe, sometimes dangerous reaction. Only certain types (known as atypical antipsychotics) should ever be considered, and even then, only with real caution and specialist input.

If a person with DLB is ever prescribed a new medication, in any care setting, including hospital, it's worth making sure the prescriber knows about the DLB diagnosis specifically, not just "dementia" as a general label. This is worth writing down and keeping in the kind of emergency information sheet covered in our Emergency Information Checklist.

What treatment and support actually looks like

There's no cure, but there's real support available. Some of the same medications used in Alzheimer's can help with the cognitive symptoms of DLB, including reducing distressing hallucinations and improving concentration, though they're most effective in the early to mid stages and don't help everyone. Therapies like physiotherapy, occupational therapy and speech and language therapy can support mobility, daily activities and communication as symptoms develop. Treatment plans are usually reviewed regularly, since symptoms in DLB tend to change over time.

A word from The Care Compass

If you're reading this because something about a dementia diagnosis has never quite matched what you're actually seeing at home, the fluctuating good and bad days, the hallucinations that seem oddly specific, the movement changes nobody quite explained, you're not imagining that gap. Lewy body dementia is common enough that it's worth naming directly and asking about, not something you should have to stumble across on a forum after the fact.

This article is for general guidance only and does not constitute medical advice. If you have concerns about a medication reaction, contact 999 in an emergency, or 111 for urgent but non-emergency concerns.

You don’t have to navigate it alone.