Hallucinations Algorithm

Safety

Red Flags — Immediate Risk and Organic Emergencies

Done

Always prioritise: Is the patient (and everyone else) safe right now? Then: is there an organic cause? Check glucose, observations and conscious level before assuming a psychiatric illness. Do not describe hallucinations as psychiatric until delirium, intoxication, withdrawal and neurological causes have been considered. Then sort into one of four pathways: delirium/medical emergency · alcohol/substance withdrawal · first-episode psychosis · sensory-release/neurological.

Command hallucinations to harm Assess and document content, intent, plan, access to means, perceived ability to resist, recent acts or preparations, suicidal or homicidal thoughts, intoxication/withdrawal, psychosis, mood disorder, capacity, protective factors and supervision. Urgent crisis assessment where there is intent, a plan, inability to resist commands, severe distress, impaired judgement, lack of safe supervision or risk to another person. 999 for imminent danger or inability to maintain immediate safety. Do not leave the person alone while arranging help. Consider safeguarding where another person may be at risk

Fever + hallucinations or confusion Encephalitis (viral or autoimmune) or meningitis — headache, neck stiffness, seizures, behaviour change → 999. Hospital will start IV aciclovir empirically if viral encephalitis is possible

Alcohol withdrawal Alcoholic hallucinosis (may occur with clear consciousness) is not the same as delirium tremens (confusion, disorientation, agitation, autonomic overactivity, hallucinations). Hallucinations during withdrawal need same-day clinical assessment. Admit if confusion/delirium, severe autonomic overactivity, seizure, high risk of seizures/DTs, significant medical or psychiatric comorbidity, or unsafe community circumstances (NICE CG100). Clear-consciousness hallucinosis may be managed through an urgent alcohol-treatment pathway only if clinically stable and safe — not a routine GP appointment

Visual hallucinations + new confusion Possible delirium — assess for acute change or fluctuation in attention, awareness, cognition, behaviour and physical function (hallucinations alone do not define delirium; they also occur in hypoactive delirium). Use the 4AT where appropriate and locally supported, but make the diagnosis clinically. If delirium cannot be distinguished from dementia, manage delirium first → find and treat the cause (NICE CG103)

Recently started or changed medicine Levodopa and dopamine agonists, anticholinergics, opioids, steroids, mefloquine, aciclovir in renal impairment → same-day medication review

Suspected Wernicke's encephalopathy Confusion, ataxia or eye-movement abnormalities in a heavy drinker or malnourished person — the full triad is uncommon and absence of one feature does not exclude it → emergency hospital assessment; parenteral thiamine per local protocol for at least 5 days unless excluded, without delaying for imaging or bloods; oral thiamine after the parenteral course (NICE CG100)

Severe agitation Unable to assess safely → withdraw, call 999 and request police support if there is immediate risk

Head injury Hallucinations or behaviour change after a head injury → same-day emergency department assessment where NICE NG232 risk factors are present (GCS <15, loss of consciousness, focal deficit, seizure, suspected skull fracture, amnesia, persistent headache, vomiting, anticoagulant or relevant antiplatelet therapy, abnormal behaviour or deterioration); CT according to the formal NG232 criteria

Parkinson's or Lewy body disease New hallucinations may reflect medication, infection or disease progression → review drugs with the Parkinson's team (do not reduce dopaminergics without balancing risks of worsening motor function, severe rigidity, akinetic crisis and neuroleptic malignant-like reactions); antipsychotics can cause severe sensitivity reactions (NICE NG97, 2018)

NG12 Progressive neurological loss Hallucinations (often olfactory or visual) with progressive, sub-acute loss of central neurological function — personality change, weakness, visual field loss, new seizures → in adults, consider urgent direct-access MRI brain, within 2 weeks (NICE NG12 (updated April 2026), rec 1.9.1). Children and young people with newly abnormal cerebellar or other central neurological function → consider very urgent referral (appointment within 48 hours). Do not use hallucinations alone as an NG12 MRI criterion

Postpartum onset New hallucinations, psychosis or mania in the weeks after birth → possible postpartum psychosis, a psychiatric emergency → immediate referral to secondary mental health services, preferably specialist perinatal, for assessment within 4 hours (NICE CG192). Do not leave the person alone; assess risk to mother and baby; 999 if immediate danger

Hallucinations are a symptom with a wide differential, and the dangerous causes sit on both sides of it: acute psychiatric risk (command hallucinations, suicidal or violent intent) and acute medical illness (encephalitis, delirium, withdrawal, intracranial lesions). Herpes simplex encephalitis carries a high mortality and outcome depends on starting aciclovir early, so fever with new psychiatric symptoms is a hospital problem. Alcohol withdrawal states can progress to seizures and delirium tremens. People with Parkinson's disease or dementia with Lewy bodies can react severely to antipsychotics, which is why their hallucinations are managed with specialist advice rather than a standard antipsychotic prescription.

Diagnose

Characterise the Hallucination — Modality and Context

Done

The modality is the most useful first question, followed by insight, timing and associated features. A hallucination is a perception without a stimulus; an illusion is a misperception of a real one.

Auditory

Voices talking to the person (second person), about them (third person, running commentary) or giving commands. Third-person voices and running commentary suggest schizophrenia; derogatory second-person voices fit psychotic depression; musical hallucinations are often associated with hearing loss but may also occur with neurological disease, psychiatric illness and medication effects

Visual

Complex (people, animals, faces) → Lewy body dementia, Parkinson's medication, Charles Bonnet syndrome, delirium, drugs. Simple (flashes, zigzags, shapes) → migraine aura, occipital seizures, retinal problems (new flashes and floaters need same-day eye assessment for retinal tear)

Tactile

Crawling under the skin (formication) → stimulants, alcohol withdrawal. Sexual or bodily interference with a delusional explanation → psychosis

Olfactory / gustatory

Brief stereotyped unpleasant smell or taste with déjà vu or a rising epigastric feeling → focal (temporal lobe) seizures — recurrent stereotyped episodes need urgent referral to a first-seizure clinic, seen within 2 weeks (NICE NG217); advise not to drive pending assessment (DVLA). These modalities point towards an organic cause; an isolated smell hallucination does not by itself need urgent MRI

Insight

Knows the experiences are not real (Charles Bonnet, hypnagogic, migraine) → lower acute risk. Believes them and acts on them (psychosis, delirium) → higher urgency

Timing

Only when falling asleep or waking (hypnagogic, hypnopompic) · only during substance use or withdrawal · evening worsening (delirium, Lewy body) · continuous through the day (psychosis)

Associated

Delusions, thought disorder, mood change, cognitive decline, parkinsonism, visual or hearing loss, headache, seizures, weight loss

Modality narrows the field quickly. Visual hallucinations in an older person are organic until proven otherwise, and in someone with poor vision, intact cognition and full insight Charles Bonnet syndrome is the likely explanation — but only after delirium, drugs and early Lewy body disease have been considered. Olfactory and gustatory hallucinations should prompt thought about focal seizures and structural lesions. Third-person voices and running commentary are classic features of schizophrenia. Hallucinations on falling asleep or waking are common in healthy people and, on their own, need explanation rather than investigation. Asking about insight and whether the person has acted on the experiences is also a risk question.

Diagnose

Differential Diagnosis by Pathway

Done

Psychiatric (first-episode psychosis pathway)

Consider only once delirium, intoxication, withdrawal and neurological causes have been considered. Schizophrenia and other primary psychoses (mainly auditory, with delusions), psychotic depression (mood-congruent voices of guilt or worthlessness), mania, severe PTSD (intrusive re-experiencing — distinguish from true hallucinations)

Neurological

Dementia with Lewy bodies (well-formed visual hallucinations, fluctuating cognition, parkinsonism, REM sleep behaviour disorder), Parkinson's disease (medication-related, often at night), focal seizures, migraine aura, brain tumour, stroke, narcolepsy (sleep-onset hallucinations with daytime sleepiness and cataplexy)

Substance-related

Intoxication: cannabis (especially high-potency), cocaine, amphetamines, LSD, psilocybin, ketamine. Withdrawal: alcohol, benzodiazepines. Heavy alcohol use: Wernicke's encephalopathy

Delirium / metabolic

Infection, hypoxia, hypoglycaemia, hyponatraemia, hypercalcaemia, hepatic or uraemic encephalopathy, thyroid disease

Drug-induced

Levodopa, dopamine agonists, amantadine, anticholinergics, opioids, corticosteroids, mefloquine, aciclovir or valaciclovir with renal impairment

Sensory / benign

Charles Bonnet syndrome (sight loss, formed images, insight retained), musical hallucinations (often hearing loss; also neurological, psychiatric or medication causes), hypnagogic and hypnopompic experiences, bereavement (sensing, seeing or hearing the person who died)

Dementia with Lewy bodies deserves special attention because the diagnosis changes prescribing: NICE NG97 (2018) recommends donepezil or rivastigmine for mild to moderate disease and warns that antipsychotics can worsen motor features and cause severe sensitivity reactions. Bereavement experiences are common and usually comforting; they should be normalised, not medicalised, unless there are other features of psychosis or complicated grief. PTSD flashbacks are vivid re-experiencing of trauma, not new perceptions, and respond to trauma-focused psychological treatment. Anti-NMDA receptor encephalitis typically presents in young adults, more often women, with psychiatric symptoms followed by seizures, dyskinesia or reduced consciousness; some cases are associated with ovarian teratoma, and it is treatable.

Diagnose

Targeted Examination

Done

Mental state exam

Appearance, behaviour, speech, mood and affect, thought form and content (delusions, suicidal or violent ideas), perception, cognition, insight. Record verbatim what the voices say

4AT

Alertness (clearly abnormal = 4) + AMT4 (0 / 1 / 2) + months backwards (0 / 1 / 2) + acute change (yes = 4). ≥4 possible delirium ± cognitive impairment → Delirium pathway. Validated mainly in hospital and long-term-care settings; use where locally supported by trained clinicians — a score is not itself a diagnosis

Cognition

If gradual decline: structured test (6CIT, MoCA). Attention and visuospatial problems out of proportion to memory suggest Lewy body disease

Neurological

Parkinsonism (bradykinesia, rigidity, tremor), focal signs, visual fields, fundi (papilloedema), gait, nystagmus and ataxia (Wernicke's)

Observations

Temperature, pulse, BP, RR, SpO₂, capillary glucose

Withdrawal signs

Tremor, sweating, tachycardia, agitation. A structured withdrawal scale (for example CIWA-Ar) supports assessment; confusion, ataxia or eye-movement signs (any one) → emergency admission and parenteral thiamine per local protocol (NICE CG100)

Vision and hearing

Visual acuity each eye, known eye disease (macular degeneration, glaucoma, cataract, diabetic retinopathy), hearing and wax

The mental state examination separates primary psychosis (clear consciousness, orientated, delusions) from delirium (fluctuating attention, disorientation) and from sensory syndromes (insight, normal cognition). The 4AT supports, but does not replace, a clinical diagnosis of delirium; its evidence base is mainly from hospital and long-term-care settings, and it uses the same scoring on the Delirium and Confusion algorithms. Wernicke's encephalopathy seldom shows the complete triad of confusion, ataxia and eye signs, so any of these in a heavy drinker or malnourished person warrants parenteral thiamine; NICE CG100 advises continuing it for at least 5 days unless Wernicke's is excluded. Parkinsonism in a person with visual hallucinations should raise Lewy body disease before any antipsychotic is considered.

Diagnose

Investigations

Done

Bloods — new presentations

FBC U&E Calcium LFTs TFTs CRP Glucose B12 / folate — clinically targeted: capillary glucose; CRP/ESR where inflammatory/infective disease is plausible; B12/folate where deficiency is plausible; urine testing where infection or renal disease is suspected; pregnancy test where relevant. HIV and syphilis serology risk- and presentation-based, with consent and pre/post-test support

Urine drug screen

Not routinely required in every presentation. If used: obtain consent, explain limitations and interpret within the clinical context. A positive result does not prove causality and does not exclude a coexisting primary psychosis; a negative one does not exclude synthetic cannabinoids or other novel substances

Suspected encephalitis

Hospital work-up: MRI, LP, EEG, autoimmune antibodies (including anti-NMDA receptor). Arranged through emergency or neurology services, not from primary care

Suspected seizures

Stereotyped episodes with olfactory or gustatory aura, déjà vu or altered awareness → refer urgently to a first-seizure clinic, to be seen within 2 weeks (NICE NG217); EEG and MRI are arranged there. Advise not to drive until assessed (DVLA)

Neuroimaging

CT head per NICE NG232 criteria after head injury, or same day for new focal signs (sudden-onset focal deficit = suspected stroke → 999). Hallucinations alone are not an NG12 criterion. NG12 adults with progressive, sub-acute loss of central neurological function → consider urgent direct-access MRI brain within 2 weeks (NG12 rec 1.9.1)

Not routinely

EEG, MRI or antibody screens in a straightforward first episode of psychosis without neurological features — the EIP team decides on further tests after assessment

Blood tests find the silent metabolic causes — hyponatraemia, hypercalcaemia, hepatic and renal failure, thyroid disease and B12 deficiency — and give a baseline if an antipsychotic is later started. A drug screen informs the conversation about substance use but does not settle the diagnosis, because substance use and primary psychosis often coexist. Anti-NMDA receptor encephalitis is worth knowing because it presents first to GPs and psychiatrists and is treatable with immunotherapy; seizures, abnormal movements, autonomic instability or reduced consciousness in a young person with new psychosis should prompt emergency neurology input. Structural imaging is for focal, progressive or atypical presentations rather than routine for every hallucination.

Refer

Referral Pathway

Done

999

Command hallucinations with intent and imminent risk, suspected encephalitis or meningitis (fever with hallucinations or confusion), delirium with unsafe behaviour, withdrawal seizures, reduced consciousness, sudden-onset focal deficit (suspected stroke), suspected Wernicke's

Same-day

New delirium without a clear treatable cause, alcohol withdrawal with hallucinations (same-day assessment; admit per CG100 criteria), other new focal neurology, head injury, crisis team for high-risk psychotic presentations; postpartum onset → perinatal mental health assessment within 4 hours (NICE CG192)

Urgent — EIP

Refer suspected first-episode psychosis without delay to local EIP/Crisis services, while arranging urgent medical assessment if delirium, intoxication, withdrawal or neurological disease remains possible — do not delay referral to complete a specialist organic work-up. EIP is open to all with a first episode, irrespective of age or duration of untreated psychosis (NICE CG178). Adults should start treatment within 2 weeks of referral where the access standard applies (NICE QS80); referral routes follow local pathways. Under 18: urgent specialist CAMHS or EIP referral according to age and local arrangements; assessment within 4 hours if referred in crisis (NICE CG155, 2013, updated 2016)

NG12

Adults: progressive, sub-acute loss of central neurological function → consider urgent direct-access MRI brain within 2 weeks (NG12 rec 1.9.1). Children and young people: newly abnormal cerebellar or other central neurological function → consider very urgent referral (within 48 hours)

Neurology

Suspected focal seizures, suspected Lewy body disease with prominent parkinsonism, narcolepsy, post-encephalitis follow-up

Old-age psychiatry / memory service

Dementia with hallucinations, suspected Lewy body dementia → specialist assessment before any antipsychotic

Ophthalmology / optometry

Charles Bonnet syndrome with untreated or changing sight loss; new flashes, floaters or field loss → same-day eye assessment

No referral

Hypnagogic or hypnopompic experiences alone, bereavement experiences without other psychotic features, typical, stable Charles Bonnet syndrome with insight — explain, reassure, optimise vision and safety-net; arrange optometry/ophthalmology for new, changing or untreated visual loss, flashes/floaters, field loss, eye pain or diagnostic uncertainty, and screen for delirium and cognitive impairment where appropriate

Charles Bonnet syndrome needs explanation more than referral: people often fear they are "going mad" and are relieved to hear it is the brain's response to reduced visual input; treating the eye condition where possible can reduce the hallucinations. Early Intervention in Psychosis services are designed to be accessed without delay, and the 2-week standard in QS80 reflects evidence that a shorter duration of untreated psychosis improves outcomes. Before any antipsychotic in dementia, specialist review is essential: the MHRA has warned (Drug Safety Update, March 2009) that antipsychotics are associated with increased cerebrovascular events and mortality in older people with dementia, and NG97 restricts their use to severe distress or risk of harm.

Treat

GP Management — by Pathway (delirium · withdrawal · psychosis · sensory/neurological)

Done

Delirium

Treat the underlying cause

Glucose, antibiotics, fluids, stop culprit drugs, non-drug care. Treat reversible causes first (pain, urinary retention, constipation, hypoxia, medication effects) and use verbal and non-verbal de-escalation. Only if de-escalation is ineffective or inappropriate and the person is distressed or a risk to themselves or others: short-term haloperidol (usually ≤1 week, lowest clinically appropriate dose — NICE CG103; MHRA), after ECG and correction of electrolyte abnormalities where appropriate. Avoid in Parkinson's disease and dementia with Lewy bodies. Same approach as the confusion and delirium algorithm.

Alcohol withdrawal

Hospital-based regimen

Withdrawal with confusion or delirium tremens is managed in hospital; any hallucinations in withdrawal need same-day assessment (admit per CG100 criteria) — never a routine GP appointment. Delirium tremens: oral lorazepam first-line in hospital (NICE CG100) — not a GP-prescribing protocol. Do not initiate a benzodiazepine withdrawal regimen in routine primary care unless part of a commissioned, medically supervised alcohol-withdrawal service with appropriate monitoring. Do not use haloperidol alone for withdrawal delirium; if hallucinations persist despite adequate benzodiazepine treatment, seek specialist/critical-care advice. Suspected Wernicke's: parenteral thiamine per local protocol for at least 5 days, then oral. Do not manage DTs at home.

Drug-induced

Stop or reduce the culprit

In Parkinson's disease, adjust dopaminergic drugs only with the Parkinson's specialist team (NICE NG71, 2017) — hallucinations may be managed through a cautious, specialist-led medication sequence; abrupt reduction risks worsening motor function, severe rigidity, akinetic crisis and neuroleptic malignant-like reactions. Review steroids and anticholinergics; check renal function for aciclovir. Hallucinations should settle over days to weeks.

PsychosisDo not start an antipsychotic for a first presentation of sustained psychotic symptoms in primary care unless it is done in consultation with a consultant psychiatrist (NICE CG178). The drug is chosen with the person, weighing side effects. GP role: assess immediate risk, exclude delirium/medical emergency, baseline observations and relevant bloods (weight, waist, BP, pulse, glucose/HbA1c, lipids, prolactin), movement-disorder assessment, ECG where indicated by the SPC, cardiovascular risk or inpatient status, and urgent EIP/crisis referral. See the psychosis algorithm.

Focal seizuresAntiseizure medicine is started by the specialist after diagnosis. Valproate is subject to MHRA pregnancy prevention requirements and should not be started by a GP.

Lewy body dementiaDonepezil or rivastigmine for mild to moderate disease (NICE NG97, 2018), started on specialist advice; they may reduce hallucinations. Antipsychotics only for risk of harm or severe distress from hallucinations/delusions, after non-drug measures and assessment for physical causes, with specialist input — sensitivity reactions can be severe and prolonged. Consider donepezil or rivastigmine in severe disease.

Charles BonnetExplanation, optimise vision and lighting, coping techniques (moving the eyes, changing activity or lighting). No medication usually needed.

Next steps: see Psychosis and schizophrenia · Dementia · Parkinson's disease · Harmful drinking and alcohol dependence

The cause dictates the treatment: an antipsychotic helps primary psychosis but can harm someone with Lewy body disease and does nothing for Charles Bonnet syndrome or withdrawal. NICE CG178 is explicit that GPs should not start an antipsychotic for a first presentation of sustained psychosis without a consultant psychiatrist's involvement, because the choice of drug and monitoring plan belong to the specialist team. In Parkinson's disease, hallucinations often reflect medication load, but the dopaminergic regimen should be changed only with the specialist team. Thiamine is given parenterally in suspected Wernicke's because absorption is unreliable in heavy drinkers, and CG100 recommends doses at the upper end of the BNF range.

Lifestyle

Patient and Carer Support

Done

Explanation Name the experience and its likely cause. For Charles Bonnet, grief or sleep-onset experiences: "Your brain is filling in gaps — this is not a sign that you are losing your mind."

Cannabis Frequent high-potency cannabis use is associated with increased risk of psychotic disorder, particularly in people with vulnerability or a family history — an epidemiological association, not an individual risk estimate. Offer non-judgemental harm-reduction and drug-service support

Other substances Stimulants and hallucinogens cause hallucinations in intoxication and withdrawal. Harm-reduction approach and community drug and alcohol service

Sleep Severe sleep loss lowers the threshold for perceptual disturbance. Regular routine; CBT for insomnia rather than hypnotics

Carer support Hallucinations in dementia are distressing for carers. Explain, advise not to argue with the experience, offer a carer's assessment and signpost to the Alzheimer's Society or Lewy Body Society

Safe environment Good lighting (shadows trigger misperceptions), less clutter, familiar people, reduced noise; avoid restraint

Vision and hearing Eye review and treatment and low-vision services may reduce visual experiences. For musical hallucinations: assess hearing and wax, review medication, assess cognition and mood, and refer for audiological/ENT assessment where hearing impairment is present — hearing aids will not necessarily stop them

Support lines Mind infoline 0300 123 3393; Samaritans 116 123 (24 hours); Hearing Voices Network groups; RNIB for Charles Bonnet information

Many people do not volunteer hallucinations for fear of being thought mad; a matter-of-fact question and a clear explanation often relieve most of the distress, especially in Charles Bonnet syndrome and bereavement. Frequent high-potency cannabis use is associated with increased risk of psychotic disorder in population studies (Di Forti et al., 2019), particularly in people with vulnerability or a family history; avoid using a single odds ratio as a patient-specific risk estimate. Improving lighting and vision addresses the trigger in sensory-deprivation syndromes. Carers of people with dementia who hallucinate need practical advice — acknowledging the experience without arguing about it — and support for themselves, because carer breakdown is a common route to crisis admission.

Safety

Follow-Up and Safety-Netting

Done

1–2 weeks

Are the hallucinations settling? Cause treated? New features? Reassess risk. Confirm the EIP, memory or neurology referral has been received and acted on

4–6 weeks

Drug-induced: resolved after the change? Delirium: fully cleared? If not, rethink the diagnosis and consider further assessment

Ongoing (psychosis)

Shared care with CMHT/EIP — physical health monitoring at least annually in primary care (NICE CG178), side effects, adherence. See the psychosis algorithm

Lewy body dementia

Specialist advice for any agitation or distressing hallucinations; non-drug measures first; antipsychotics only for severe distress or risk (NICE NG97)

Driving

Possible focal seizures or recurrent altered-awareness episodes: advise not to drive until assessed — specific DVLA seizure rules apply. Unexplained hallucinations alone do not automatically require DVLA notification. Active psychosis may affect fitness to drive depending on severity, insight, treatment and functional impact. Medication-related sedation or impaired judgement may make driving unsafe. Use current DVLA guidance (neurological disorders; psychiatric disorders; drug or alcohol misuse)

Documentation

Record the modality, content (in the patient's words), insight, risk assessment, capacity where relevant, who was told, and the agreed follow-up date

Capacity & safeguarding

Assess decision-specific capacity where the person declines assessment or treatment; act in best interests under the Mental Capacity Act where capacity is lacking, or use Mental Health Act routes via the crisis team. Raise a safeguarding concern where children, vulnerable adults or other identified people may be at risk

999 safety-net

Voices telling them to harm themselves or others and they feel they might act, fever with confusion, fit, collapse, sudden loss of vision

Same-day GP

Hallucinations worsening, new weakness or unsteadiness, unable to look after self, carer unable to cope, new confusion

Wording

"If the voices start telling you to hurt yourself or anyone else, or you feel you can't keep yourself safe, call 999 or go to A&E. You can also call NHS 111 and choose the mental health option, or the crisis number we've given you."

The key follow-up question after stopping a suspected culprit drug is whether the hallucinations resolved; if not, a primary neurological or psychiatric cause is more likely and needs pursuing. Risk is dynamic, so it should be reassessed at every contact rather than documented once. Wernicke's encephalopathy can develop during any period of poor intake in a heavy drinker, including after admission, so recurrence of confusion, unsteadiness or eye signs needs emergency hospital assessment (999). For the SCA, examiners reward explicit, specific safety-netting with named routes (999, NHS 111 mental health option, crisis line), a follow-up date, and attention to the carer.