In the body alcohol causes excitation of the brain, loss of inhibition and relief of tension and anxiety at low doses, but depresses the mood at higher doses, sedates, impairs concentration, slows reflexes, impedes learning and memory, decreases co-ordination, slurs speech, changes sensation, weakens muscles and increases production of urine.
Other effects may include abnormalities of the blood chemistry, nausea and vomiting. Self-injury as a result of falls and other accidents is very common amongst those affected by alcohol.
Long-term abuse of alcohol (alcoholism) may have other serious effects on the brain, liver and other organs.
Levels of alcohol above 0.05% are considered sufficient to have significant adverse effects and impair driving.
Actual legal levels of alcohol in the blood vary from country to country.
Alcohol withdrawal (hangover) may cause tremor, headache, loss of appetite, nausea, sweating and insomnia. If the use of alcohol has been long term, withdrawal may cause delirium tremens.
When measuring blood alcohol levels doctors divide the results as follows: –
- Over 0.05 g/100 mL (over 11 mmol/L) – Reflexes impaired. Legally liable in some countries.
- From 0.08 to 0.3g/100 mL (17 to 66 mmol/L) – Stuporous
- From 0.3 to 0.4 g/100 mL (66 to 110 mmol/L) – Comatose
- Over 0.4 g/100 mL (over 110 mmol/L) – Potentially fatal
A breathalyser makes an estimate of the blood alcohol level by measuring the amount of alcohol from a breath.