Medically reviewed guide · Last updated: 9 November 2026 · Reading time: approx. 11 min

Sudden Confusion: Delirium, Stroke or Medication?

The most common causes compared

The causes in detail

This article is about acute confusion: someone who was perfectly clear yesterday no longer recognises their own home today, talks incoherently, is restless at night or unusually drowsy. If, on the other hand, someone has been forgetting names and appointments for months, you will find guidance in our article on forgetfulness, and background on gradual memory loss under dementia. The difference matters: acute confusion is almost always the result of a treatable physical cause — and it calls for an examination the same day.

What defines delirium

Delirium (classified under F05 in the ICD-10) is an acute disturbance of brain function. Its hallmarks are a rapid onset, impaired attention — the person cannot follow a conversation and drifts off —, muddled thinking and a fluctuating course: in the morning someone seems almost normal, in the evening they do not recognise their relatives. The day-night rhythm is often disturbed, and some people see things that are not there. The restless (hyperactive) form, with wandering, calling out and fidgeting, is noticed straight away. The quiet (hypoactive) form is common in older people and treacherous: they lie listlessly in bed, barely eat or drink and are thought to be “just tired” or “depressed”. Risk factors are older age, poor sight or hearing, many medicines, serious illness and, above all, existing dementia — in which delirium is missed particularly often because the deterioration is put down to the dementia.

Infections

In older people, confusion is sometimes the first or only sign of an infection — fever may be absent. Classic examples are a urinary tract infection and pneumonia, but also wound infections or blood poisoning (sepsis). A fast pulse, rapid breathing, cold, mottled skin and increasing drowsiness point to sepsis and are an emergency. Important: an abnormal urine dipstick test in an older person does not automatically prove that the bladder is the cause — bacteria in the urine without symptoms are common. The practice weighs this up against other causes.

Dehydration and salt balance

Older people feel thirst less strongly, deliberately drink less in hot weather or because of incontinence, and lose fluid quickly with diarrhoea or fever. Dehydration (exsiccosis) causes drowsiness and confusion and puts a strain on the kidneys. An underestimated cause is a low sodium level in the blood (hyponatraemia): it often develops gradually and shows up as confusion, unsteady gait, nausea and falls. Common triggers are water tablets, certain antidepressants and anti-epileptic drugs — a blood test will clarify this. How heat and medicines interact is explained in our guide Medications and heat.

Metabolism, oxygen and organs

Low blood sugar on insulin or sulfonylureas causes confusion within minutes, often with sweating and trembling; very high blood sugar levels in poorly controlled diabetes also cloud consciousness. Too little oxygen or too much carbon dioxide in the blood — for example during an acute flare-up of COPD, in heart failure or pneumonia — has a similar effect. Severe liver or kidney disease, thyroid disorders, marked vitamin B12 deficiency and carbon monoxide poisoning, for example from a faulty gas boiler, are less common but belong in the work-up. Pain, urinary retention or severe constipation can also trigger or worsen delirium in older people.

Surgery and hospital

After operations — especially after a hip fracture or major surgery — older people often develop delirium. Anaesthesia, pain, painkillers, lack of sleep, unfamiliar surroundings and missing glasses or hearing aids all play a part. This kind of delirium can last for days to weeks and is often first noticed by relatives. Before planned procedures it is worth raising the risk of delirium; tips are in our guide Medications before surgery.

Alcohol: withdrawal delirium and vitamin B1 deficiency

Anyone who drinks heavily on a regular basis and suddenly stops — during a hospital stay, for instance — can develop withdrawal delirium (delirium tremens), usually two to three days after the last drink: trembling, sweating, racing heart, agitation, hallucinations and seizures. This is life-threatening and needs hospital treatment. A lack of vitamin B1 (thiamine) in alcohol dependence or severe malnutrition can cause Wernicke’s encephalopathy — confusion, unsteady gait and disturbed eye movements. It is treated with thiamine, ideally before any sugar is given.

When the brain itself is affected

A stroke usually shows up as paralysis, a drooping corner of the mouth or a speech disturbance. Some strokes, however, mainly disrupt the understanding of language — the person speaks fluently but makes no sense and seems “confused”. Our article on word-finding difficulties helps to tell these apart. After a fall, blood can slowly collect under the tough outer membrane of the brain (subdural haematoma), especially in people on blood thinners — the confusion then sometimes only begins days or weeks later. Other causes include an epileptic seizure followed by a period of clouded consciousness, inflammation of the meninges or the brain with fever and headache, and rarely a brain tumour.

Special case: suddenly “wiped”

In transient global amnesia, a person — usually older — loses the ability to retain new information for a few hours. Typically they ask the same questions over and over (“What day is it today?”), but know who they are and can move and speak normally. The disorder usually resolves completely within 24 hours and is considered harmless. Because a stroke or a seizure can start in a similar way, it still needs to be assessed by a doctor immediately.

Self-checks: first clues for relatives

People who are confused often cannot assess themselves — these checks are therefore meant for relatives and carers. They do not replace a medical examination or a diagnosis, but they help you judge the situation and give the ambulance service or the practice concrete observations.

• Comparison with usual: When was the person last “their normal self”? Have they been different for hours, days or for months already? A clear turning point suggests an acute cause.
• The attention test: Ask the person to say the months of the year backwards, starting with December. If they falter or get mixed up after only a few months although they normally manage easily, they have a problem with attention — a core sign of delirium. Similar tasks are part of short tests such as the 4AT, which hospitals use.
• Orientation: Does the person know their age, date of birth, where they are and the current year?
• The stroke check (FAST): Face — ask them to smile: does one corner of the mouth droop? Arms — stretch both arms out in front: does one drift down? Speech — repeat a simple sentence: is it slurred or meaningless? Time — if anything is abnormal, call 112 immediately.
• Blood sugar, fever, fluid intake: In people with diabetes, measure blood sugar straight away; values below 70 mg/dl (3.9 mmol/l) suggest low blood sugar. Take their temperature and note how much they have drunk over the last few days and whether they have passed urine.
• The medication check: What has been started, increased or stopped in the last two weeks — including over-the-counter sleeping or travel sickness tablets? Do the blister packs match the plan, or have doses been taken twice? Take the packs or the medication plan with you to the doctor or hospital.

Warning signs: when you should not wait

Sudden confusion is always a reason for a medical examination the same day — through the GP practice or, in the evening and at weekends, through the out-of-hours medical service (116 117). With these signs it is an emergency:

• Paralysis or numbness on one side of the body, a drooping corner of the mouth, speech or vision problems — see also one-sided weakness
• Fever with a stiff neck, severe headache or skin spots
• Confusion after a fall or a blow to the head, especially on blood thinners
• Increasing drowsiness, hardly rousable, seizure
• Breathlessness, bluish lips, a very fast pulse or cold, mottled skin
• Low blood sugar that does not improve quickly after glucose
• Trembling, sweating and hallucinations after giving up alcohol or after stopping sedatives
• Suspected overdose or poisoning, including carbon monoxide

The treatment pathway: step by step

1. Safety first. Check for emergency signs; if in doubt, call 112. Do not leave the person alone, secure trip hazards and the cooker, and do not let them drive. Speak calmly and in short sentences; do not contradict or argue.
2. Medical assessment the same day. The practice or hospital measures blood pressure, pulse, temperature, oxygen and blood sugar, carries out a neurological examination and takes blood: inflammation markers, sodium, kidney and liver values, blood count. Depending on the findings, a urine test, chest X-ray, ECG and brain imaging are added. Bring a complete list of medicines and your observations.
3. Treat the cause. This is the actual treatment of delirium: treating the infection, correcting fluid and salt balance, relieving pain, resolving urinary retention and constipation, reducing or replacing triggering medicines. Often there are several triggers at the same time.
4. Non-drug delirium care. Familiar people, glasses and hearing aids, a clock and calendar in view, daylight during the day and quiet at night, early mobilisation, enough to drink and eat. Restraints and urinary catheters are avoided wherever possible. Many hospitals allow relatives longer visiting hours in cases of delirium.
5. Medicines only where targeted. If severe agitation or hallucinations put the person at risk, the treating doctor may use an antipsychotic briefly and at a low dose. Benzodiazepine-type sedatives are generally unfavourable in delirium — the exception is delirium from alcohol or benzodiazepine withdrawal. In Parkinson’s disease or dementia with Lewy bodies, many antipsychotics are dangerous. The decision always lies with the treating practice or hospital.
6. Follow-up. Delirium can have after-effects for weeks. A few weeks after recovery, have memory and everyday abilities checked again and the medication plan reviewed — it is worth taking a close look at the discharge planning from hospital, see After hospital discharge.

The medication angle: when tablets cause confusion

Medicines are among the most common and most easily remedied triggers of delirium. Older brains react more sensitively, the kidneys and liver break down drugs more slowly, and the risk rises with every additional active substance. The PRISCUS 2.0 list (a German list of potentially inappropriate medication) names active substances that are particularly unsuitable for older people.

Drugs with anticholinergic effects

Many active substances block the messenger substance acetylcholine, which is important for attention and memory. They include older antidepressants such as amitriptyline, bladder medicines such as oxybutynin, over-the-counter sleeping and travel sickness remedies containing diphenhydramine, doxylamine or dimenhydrinate, scopolamine (hyoscine) patches and some Parkinson’s and allergy medicines. Individually often harmless, their effects add up — our guide Anticholinergic burden explains how to estimate this. Dry mouth, constipation and urinary retention are typical companions.

Sleeping pills and sedatives

Benzodiazepines such as lorazepam or diazepam and Z-drugs such as zolpidem can trigger confusion, night-time wandering and falls in older people. At the same time, stopping them abruptly after longer use leads to withdrawal symptoms up to and including delirium and seizures — so only taper them off, and do so under medical supervision. Gentler approaches are described in our guide Sleeping pills: what helps.

Opioids and painkillers

Opioids such as tramadol, tilidine, morphine or oxycodone can cause confusion, especially at the start of treatment and when kidney function is reduced. However, untreated pain also triggers delirium — so simply leaving out painkillers is not a solution. According to the package leaflet, over-the-counter painkillers such as ibuprofen should generally not be taken for more than three to four days in a row without medical advice; in older people they also put additional strain on the kidneys and stomach.

Cortisone, Parkinson’s medicines and anti-epileptic drugs

High-dose cortisone such as prednisolone or dexamethasone can cause restlessness, sleeplessness, mood swings and, rarely, a psychosis with confusion. Parkinson’s medicines such as levodopa and dopamine agonists more often lead to hallucinations and confusion in older people. Many anti-epileptic drugs also cause drowsiness and slowness at higher doses.

Medicines with a narrow margin

With lithium and the heart medicine digitoxin, effective and toxic levels lie close together. Dehydration, diarrhoea, anti-inflammatory painkillers or water tablets can cause the levels to rise. Warning signs with lithium are trembling, diarrhoea and confusion; with digitalis, nausea, visual disturbances with yellow vision, heart rhythm disorders and confusion. Insulin and sulfonylureas such as glimepiride cause low blood sugar; water tablets and some antidepressants lower sodium.

Antibiotics and combinations

Fluoroquinolones such as ciprofloxacin and levofloxacin can cause psychiatric side effects up to and including confusion and disorientation, especially in older people. Combinations of several serotonergic drugs — for example an antidepressant together with tramadol — can trigger serotonin syndrome: agitation, confusion, fever, sweating, trembling and muscle twitching. Which combinations are critical is shown by the interaction check.

How to help prevent delirium

Not every case of delirium can be prevented, but many triggers are known. For older people at risk, simple measures help most of all:

• Support the senses — glasses, hearing aids and dentures belong in hospital too and should be within easy reach there.
• Drink enough — especially in hot weather, with fever and diarrhoea, unless a fluid restriction has been prescribed. A full glass within sight helps.
• Declutter the medication plan — have it checked at least once a year and after every hospital stay to see whether each medicine is still needed. Background in our guide Medications in old age.
• Plan ahead before operations — raise the risk of delirium, hand over a medication list, pack familiar belongings and plan visits.
• Routine and exercise — daylight, fixed times, activity during the day and rest at night; avoid over-the-counter sleeping pills where possible.
• Avoid dosing errors — weekly pill organisers, reminders and an up-to-date plan prevent double or missed doses, a common cause of problems with medicines that need level monitoring.

Keep track of a relative’s medicines safely — with brite

Medication plan, dose reminders and observations in one place, ready for the practice and hospital. Free of charge.

Start for free