Dizziness (for Vertigo - see Vertigo)

Differential Diagnosis

Common Diagnoses

  • Viral Illness
  • Anxiety (and Hyperventilation)
  • Hypoglycaemia
  • Postural Hypotension (e.g. Elderly and Pregnancy)
  • Iatrogenic: Drug therapy (e.g. Antihypertensives, Antidepressants – May Cause Dizziness in their Own Right or Via Postural Hypotension)

Occasional Diagnoses

Rare Diagnoses

  • Carotid Sinus Syndrome
  • Aortic Stenosis
  • Subclavian Steal Syndrome
  • Partial Seizures
  • Addison’s Disease
  • Carbon Monoxide Poisoning (Blocked Flue)
  • Significant Acute Illness (e.g. Silent Infarct, Gastrointestinal Haemorrhage – Can Present with Sudden Onset Dizziness)

Ready Reckoner

Key distinguishing features of the most common diagnoses

Viral InfectionHypoglycaemiaPostural HypotensionIatrogenicAnxiety
Sudden OnsetNoYesYes PossibleNo
Irritable MoodNo PossibleNoNo Possible
EpisodicNoYesYes Possible Possible
Coincides with Start of MedicationNo Possible Possible PossibleNo
Relief on Lying DownNoNoYesYesNo

Possible Investigations


Possible:Urinalysis, FBC, U&E, LFT, glucometer blood glucose, Tilt table test.

Small Print:EEG, ECG/24-h ECG, echocardiography, CT scan, hospital-based investigations.

  • Urinalysis for glucose: Underlying diabetes may cause dizziness, either through general malaise or because of an autonomic neuropathy.
  • FBC: Underlying anaemia can cause or exacerbate light-headedness; raised MCV may indicate alcohol abuse.
  • U&E and LFT may be worth measuring if systemic disease suspected; in particular, sodium low, and potassium and urea both high in Addison’s disease; LFT may be abnormal in alcohol abuse.
  • Glucometer blood glucose: Blood glucose measurement will provide a diagnosis of hypoglycaemia only if done during an episode.
  • EEG: If partial epilepsy a possibility (would also then require CT scan) – both arranged by specialist.
  • ECG/24 h ECG: For possible arrhythmia.
  • Echocardiography: For suspected aortic stenosis.
  • Hospital-based investigations: In acute onset/unwell patient to rule out possibilities such as silent infarct or gastrointestinal haemorrhage.
  • Tilt table test: if suspicion of PoTS

Top Tips

  • The first step in the history is to establish what the patient means by dizziness, and, in particular, to distinguish it from true vertigo.
  • Dizziness is often multifactorial, especially in the elderly – so do not necessarily expect to find a single underlying pathology.
  • If no clear diagnosis is obvious from the history, the dizziness is long standing, and the patient presents a list of other vague symptoms yet is objectively quite well (e.g. no weight loss), the likely diagnosis is anxiety.
  • Don’t forget that commonly prescribed drugs can cause or aggravate postural hypotension – review the patient’s medication.

Red Flags

  • If the patient has episodic loss of consciousness as well as dizziness, then the chances of significant pathology are much greater – investigate or refer.
  • In puzzling cases, ask about other family members and type of domestic heating used. Carbon monoxide poisoning is a completely avoidable but regular killer.
  • If an aortic murmur is heard, refer urgently. Significant aortic stenosis can cause sudden death.
  • Remember denial is very strong in alcoholics. If in doubt, check MCV and LFT.
  • An acute presentation of dizziness is unusual. Beware this in the older infrequent attender, especially if the patient seems unwell – consider a silent infarct or gastrointestinal haemorrhage.
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