Reasoning GP · Algorithm · 1-page summary
Hallucinations — new presentation
For: adults and young people with new or changed hallucinations. Not for: known psychosis under follow-up (psychosis algorithm) or detailed delirium work-up (confusion and delirium algorithm). Under 18: block 4.
Core rule: safety first, then organic: check glucose, observations and conscious level, and do not call hallucinations psychiatric until delirium, intoxication, withdrawal and neurological causes have been considered.
0Stop — call 999 now — do not leave the person alone
- Command hallucinations with intent and imminent danger, or unable to keep safe → 999. Severe agitation, unable to assess safely → withdraw, 999, police support if immediate risk. Consider safeguarding.
- Fever with hallucinations or confusion (encephalitis, meningitis): headache, neck stiffness, seizures, behaviour change → 999
- Suspected Wernicke's: confusion, ataxia or eye-movement signs — any one — in a heavy drinker or malnourished person → 999; parenteral thiamine in hospital without waiting for imaging or bloods.
- Withdrawal seizures, reduced consciousness, delirium with unsafe behaviour, sudden-onset focal deficit (suspected stroke) → 999
1Triage by modality — the first question
| Modality | Points to |
|---|---|
| Auditory | Third-person, running commentary → schizophrenia; derogatory second-person → psychotic depression; musical → hearing loss |
| Visual | Complex → Lewy body, Parkinson's drugs, Charles Bonnet, delirium, drugs. New flashes or floaters → Same-day eye |
| Touch | Formication → stimulants, alcohol withdrawal |
| Smell / taste | Stereotyped, déjà vu → focal seizures → first-seizure clinic ≤2 weeks; no driving |
| Insight | Knows not real → lower risk; acts on them → higher urgency |
2Screen — one row is enough
- Command hallucinations with intent, plan, can't resist, severe distress or risk to others → Same-day crisis team
- Alcohol withdrawal with hallucinations → Same-day; admit per CG100 criteria.
- Delirium with no clear treatable cause → Same-day
- New or changed medicine (dopaminergics, anticholinergics, opioids, steroids, mefloquine) → Same-day review
- Head injury with NG232 risk factors → Same-day ED. Postpartum onset → perinatal team ≤4 h. New focal signs → Same-day
- Adults, progressive sub-acute neurological loss → consider MRI brain ≤2 weeks (NG12). Child, new abnormal neurology → consider referral ≤48 h
3Assess
☐ Temp, pulse, BP, RR, SpO₂, capillary glucose ☐ Mental state, voices' words verbatim, insight, risk ☐ 4AT (≥4 possible delirium) ☐ Parkinsonism, focal signs, fields, fundi, gait, ataxia ☐ Acuity, hearing, wax ☐ Targeted FBC, U&E, calcium, LFTs, TFTs, CRP, B12/folate; pregnancy test if relevant
Drug screen only with consent, if it informs care. No EEG, MRI or antibodies from primary care.
4Classify — only if the screen is negative
- Delirium / metabolic — fluctuating attention, disorientation → find and treat the cause.
- Drug or substance — medicine change, intoxication or withdrawal → stop or reduce the culprit.
- Lewy body / Parkinson's — well-formed visual, fluctuating cognition, parkinsonism → memory service or Parkinson's team before any antipsychotic.
- First-episode psychosis — mainly auditory, delusions, clear consciousness → Urgent EIP without delay, any age; adults start treatment ≤2 weeks. Under 18 → CAMHS or EIP; crisis seen ≤4 h.
- Sensory / benign — Charles Bonnet (sight loss, insight kept), hypnagogic, bereavement → explain and safety-net.
- Uncertain — say so, keep organic causes open, reassess risk, and name who reviews and when.
5Treat today — only these
- Delirium: treat reversible causes, de-escalate. Haloperidol only if distressed or a risk and de-escalation fails, usually ≤1 week; avoid in Parkinson's and Lewy body.
- Psychosis: no antipsychotic unless with a consultant psychiatrist (CG178). Baseline weight, waist, BP, pulse, glucose/HbA1c, lipids, prolactin.
- Alcohol: no benzodiazepine withdrawal regimen in routine primary care; never manage DTs at home.
- Charles Bonnet: explanation, better vision and lighting, coping techniques; usually no medicine. Doses: NICE/SPC, BNF, local formulary.
6Refer routinely
- Dementia with hallucinations or suspected Lewy body → memory service or old-age psychiatry before any antipsychotic.
- Neurology: Lewy body with prominent parkinsonism, narcolepsy. Optometry: Charles Bonnet with untreated or changing sight loss.
- No referral: hypnagogic experiences alone, bereavement without psychotic features, stable Charles Bonnet with insight.
7Never reassure by
- A psychiatric label before delirium, intoxication, withdrawal and neurology are considered.
- Clear consciousness in alcohol withdrawal.
- An incomplete Wernicke's triad.
- A drug screen: positive does not prove the cause; negative misses synthetic cannabinoids.
- A 4AT score in place of a clinical diagnosis of delirium.
- A standard antipsychotic in Lewy body or Parkinson's disease.
8Safety-net — say it, then document it
999 “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.” Also 999 for fever with confusion, a fit, collapse or sudden loss of vision.
Same day: “Contact us today if the hallucinations get worse, you have new weakness, unsteadiness or confusion, you can't look after yourself, or your carer can't cope.” Driving: possible focal seizures → no driving until assessed (DVLA).
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies; risk assessed
Observations and glucose normal; delirium screened
Medicines, alcohol and substances reviewed
Cause named or uncertainty stated; referral and follow-up date set
Safety-net, crisis numbers and driving advice given; who was told recorded
Summary of the full Reasoning GP hallucinations algorithm, which holds the detail, examination, investigations and evidence. Sources: NICE CG178, QS80, CG155, CG103, CG100, NG97, NG71, NG232, NG217, CG192, NG12 (updated April 2026); MHRA; DVLA. Clinical reference — follow local crisis and emergency pathways and check doses: NICE/SPC, BNF.