Physical examination and baseline investigations

01Purpose and principlesWhat the assessment is for and the core concepts behind it.

Psychiatric symptoms can be the presenting language of physical illness. Begin with timing and physiology: sudden fluctuating confusion, visual phenomena and inattention differ from a months-long stable syndrome. Review prescribed, over-the-counter and illicit substances, recent dose changes, withdrawal, overdose, infection, endocrine symptoms, seizures, head injury, reproductive state and nutritional status. Obtain observations and assess hydration, injury, infection and toxidromes. The extent of examination should reflect acuity and uncertainty, not the destination service.

The neurological examination includes attention and orientation, cranial nerves, eye movements, tone, power, reflexes, coordination, gait and abnormal movements as indicated. Look for meningism, focal deficit, parkinsonism, chorea, myoclonus, rigidity, clonus and catatonic signs. Cardiovascular examination and postural blood pressure can explain collapse or medicine adverse effects. Thyroid, hepatic, respiratory and nutritional signs may guide laboratory testing. Consider assault, self-harm and neglected physical disease, offering a chaperone and trauma-sensitive explanation.

Baseline investigations should have a question. FBC may reveal anaemia or infection; renal, liver, glucose, calcium and electrolyte testing can identify metabolic disturbance and determine prescribing safety; thyroid testing addresses compatible mood, cognitive or activation symptoms. Add B12, folate, inflammatory, infection or endocrine tests when history or phenotype supports them. Pregnancy testing may materially change investigations and prescribing but requires explanation and consent. HIV or syphilis testing should be risk based, consented and accompanied by appropriate pathways rather than used as a stigmatising routine screen.

ECG is important with overdose, syncope, stimulant use, cardiac disease, electrolyte disturbance and medicines that can prolong QT or affect conduction. Before antipsychotic treatment, obtain guideline-aligned physical and metabolic measurements where feasible: weight, waist circumference or BMI, pulse, blood pressure, glucose or HbA1c and lipids, alongside movement-disorder and lifestyle baseline. Urgent behavioural disturbance may require treatment before every measure is available; document why, then complete monitoring promptly.

Advanced tests follow red flags. CT or MRI addresses trauma, focal neurology, new seizure, atypical late onset, rapid cognitive change or suspected structural disease. EEG supports possible seizure or encephalopathy but does not exclude either when normal. Lumbar puncture and infection or autoimmune testing may be required for fever, seizures, dyskinesia, autonomic instability, catatonia or rapidly evolving psychosis. Consult neurology, acute medicine, toxicology or infectious diseases early when the syndrome crosses disciplines.

Key points

Start with vital signs, oxygen saturation, consciousness and bedside glucose when illness, intoxication, withdrawal or altered behaviour could reflect physiological disturbance.
Perform a complete examination when presentation is acute or unexplained, adding focused neurological, cardiovascular, endocrine, injury, infection and nutritional assessment from the history.
Select tests to answer stated questions; there is no universal blood panel that proves a presentation is medically cleared for psychiatric care.
Common initial tests may include FBC, renal and liver profiles, electrolytes, calcium, glucose, thyroid function and pregnancy testing when clinically relevant and consented.
Use ECG before or during medicines with cardiac or QT implications and when syncope, chest symptoms, electrolyte disturbance, overdose or stimulant exposure is possible.
Toxicology results are limited by detection windows, cross-reactivity and incomplete panels; a negative screen does not exclude substance involvement and a positive result does not prove causation.
Brain imaging, lumbar puncture, EEG, infection testing and autoimmune work-up are targeted by onset, course, examination and risk rather than ordered routinely.
Record baseline weight, waist or BMI, pulse, blood pressure and relevant metabolic markers before antipsychotic treatment where urgency permits, without delaying necessary emergency care.
Explain tests, seek consent, preserve dignity and assign responsibility for results and follow-up, including abnormalities discovered after transfer or discharge.

02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.

Delirium physiology

Fluctuation, inattention and altered arousal with infection, hypoxia, metabolic disturbance or medicine exposure indicates acute brain dysfunction requiring cause treatment.

Toxidrome

Pupil change, sweating, temperature, bowel sounds, urinary retention, clonus, rigidity or autonomic instability can identify a poisoning or withdrawal pattern.

Neurological phenotype

Focal deficit, seizure, unusual movement, ataxia, rapid cognitive loss or new severe headache supports targeted neurological investigation rather than routine psychiatric admission.

Treatment baseline need

Cardiometabolic measurements, ECG indications, movement findings and prolactin-related symptoms establish safety and allow later adverse effects to be recognised.

Diagnostic overshadowing

Pain, dyspnoea, infection or endocrine disease is attributed to a psychiatric diagnosis without equivalent physical assessment, delaying ordinary medical care.

Red flags requiring action

First psychiatric symptoms after age 40, abrupt onset, rapid progression or prominent cognitive change should lower the threshold for medical and neurological investigation.
Fever, autonomic instability, rigidity, clonus, reduced consciousness or recent psychotropic change can signal serotonin toxicity, neuroleptic malignant syndrome, withdrawal or encephalitis.
New seizure, focal signs, severe headache, head trauma, papilloedema, abnormal movements or catatonia warrants urgent neurological assessment and targeted imaging or electroencephalography.
Pregnancy, postpartum state, immunosuppression, endocrine symptoms, malnutrition or substantial substance exposure changes both differential diagnosis and test selection.
A normal screening panel cannot rule out conditions such as epilepsy, autoimmune encephalitis, early infection or intermittent intoxication when the phenotype remains concerning.

03Method and interpretationA systematic approach to the test and its findings.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Immediate observations and bedside glucoseFirst step
Why
Identify hypoxia, fever, hypotension, tachycardia, hypoglycaemia and altered consciousness requiring emergency treatment.
Interpretation and limitations
Abnormal physiology determines care setting and urgency. Normal observations reduce some risks but do not exclude evolving poisoning, seizure, encephalitis or intracranial disease.
02
History-directed physical and neurological examination
Why
Find injury, infection, toxidrome, endocrine signs, focal deficit, movement disorder and treatment complications.
Interpretation and limitations
Document positive and meaningful negative findings. Limited cooperation should be recorded with a plan to repeat, not converted into a normal examination.
03
Initial laboratory tests
Why
Assess blood count, organ function, electrolytes, calcium, glucose and thyroid status when indicated by presentation or prescribing.
Interpretation and limitations
Interpret abnormalities in clinical context and add targeted tests. A broad normal panel is not a reference standard for excluding all organic causes.
04
ECG and cardiometabolic baseline
Why
Detect conduction or QT risk and establish measures needed for safe psychotropic treatment and longitudinal monitoring.
Interpretation and limitations
Consider heart rate, correction method, electrolytes, cardiac history and interacting medicines. Missing urgent baseline data should be obtained after stabilisation with an assigned reviewer.
05
Targeted toxicology and drug concentrations
Why
Support management of suspected overdose, intoxication, withdrawal or therapeutic toxicity.
Interpretation and limitations
Detection windows and assay scope limit inference. Use specific concentrations such as paracetamol or lithium when clinically relevant and do not equate a urine result with impairment.
06
Neuroimaging, EEG or cerebrospinal-fluid studies
Why
Investigate structural disease, seizure, infection, inflammation or rapidly evolving encephalopathy when warning features exist.
Interpretation and limitations
Choose modality and timing with specialist input. Normal early results may not end investigation if the syndrome and trajectory remain discordant.

04Clinical next stepsHow the result changes management or prompts escalation.

01Acute presentationStabilise before psychiatric attributionFirst stepBehavioural or mental-state change is sudden, severe, fluctuating or accompanied by physical warning features.

1Use ABCDE, observations, glucose and focused history for medicines, substances, trauma, seizure, infection and baseline cognition.
2Perform targeted physical and neurological examination and request time-critical tests based on the suspected syndrome.
3Treat abnormalities and arrange the correct medical setting, maintaining psychiatric risk precautions and a clear cross-specialty handover.

02Baseline work-upAsk a question with each testA non-emergency psychiatric syndrome requires diagnostic clarification or treatment planning.

1Use history, age, onset and examination to define plausible medical, neurological, substance and reproductive contributors.
2Request proportionate laboratory, ECG or other investigations and explain their purpose, limitations and possible consequences.
3Integrate results into the formulation, communicate uncertainty and assign responsibility for action and repeat testing.

03Psychotropic baselineMeasure before and monitor afterAntipsychotic or another medicine with significant physical monitoring requirements is being considered.

1Record relevant weight, waist or BMI, pulse, blood pressure, glucose or HbA1c, lipids, movement symptoms and indicated ECG or prolactin information.
2Address modifiable cardiac and metabolic risk and explain adverse effects and monitoring in a supported consent discussion.
3If urgent treatment precedes complete measurement, state the reason and complete missing baseline data as soon as clinically possible.

05Risks, monitoring and follow-upComplications, safety checks and further assessment.

Track unresolved abnormal observations and results across transfers, naming the clinician or team responsible for review and escalation.
Repeat examination after sobriety, sleep, rehydration or behavioural settling when the first assessment was limited, while avoiding unsafe delay in acute treatment.
Compare cardiometabolic and movement findings with the documented pre-treatment baseline at guideline-aligned intervals and after important medicine changes.
Reopen the organic differential when symptoms progress rapidly, consciousness fluctuates, new neurological signs appear or expected treatment response is absent.
Communicate incidental findings and follow-up clearly to the patient and GP, including urgency and what should trigger earlier review.

06Special situationsVariants, exceptions and circumstances that change the usual approach.

Clearance is not a test

Suitability for psychiatric care is a clinical judgement about current stability and service capability, not a normal universal laboratory panel.

Cooperation affects certainty

An incomplete examination reduces confidence; it does not justify documenting absent signs that could not actually be assessed.

Toxicology has a window

Assays detect selected compounds or metabolites for varying periods and rarely establish the timing, dose or causal role by themselves.

Baseline protects attribution

Documenting weight, movement and endocrine symptoms before treatment helps distinguish pre-existing problems from medicine-emergent adverse effects.

Normal tests do not end thinking

Autoimmune encephalitis, epilepsy, intermittent arrhythmia and early infection may remain plausible despite an initially reassuring basic screen.

07Common pitfallsFrequent interpretation and management errors.

01
Using psychiatric history as a reason to provide less physical assessment than another patient would receive.
02
Ordering every available blood test without a clinical question or plan for abnormal results.
03
Calling a patient medically cleared solely because routine blood results are normal.
04
Interpreting a positive urine drug screen as proof that a substance caused the presentation.
05
Delaying urgent behavioural treatment solely to obtain non-critical baseline measurements.
06
Missing pregnancy, overdose, withdrawal, head injury or medicine interaction in the initial history.
07
Failing to repeat an examination that was limited by agitation or intoxication.