Published: August 1999


Too Much Caffeine

This article is more than five years old. Some content may no longer be current.

Prescriber Update 19: 28–29
August 1999

Medsafe Editorial Team

Because of the wide variety of products containing caffeine a person may be ingesting a considerable amount without being aware of it. Sources of caffeine include preparations sold to assist in fitness and sporting performance, energy drinks, soft drinks, various medicines, herbal tonics containing guarana, as well as coffee, tea and chocolate.
Caffeine overdose can cause nausea, diarrhoea, light-headedness and urinary frequency. Caffeine withdrawal even after moderate chronic intake may be associated with headache, nausea, nervousness, reduced alertness and depressed mood. Symptoms are most acute in the first 20-48 hours but they may persist for as long as seven days.

Caffeine overdose results in gastrointestinal and cardiorespiratory symptoms

A browse through shelves of ingestable products sold to assist in fitness and sporting performance will reveal that many products contain caffeine, some in quite large quantities. For some the recommended daily dose includes more than 500mg of caffeine. Caffeine may be present in these products from the herbal preparation guarana, as well as being added as pure caffeine. These products include Thermo Blast IV, Thermo Genesis2 and Energy Booster.

Those who take these preparations without reducing their regular caffeine intake from other sources may risk developing what has been termed "caffeinism" which is caused by toxic levels of caffeine. The symptoms include nausea, diarrhoea, indigestion, irregular heartbeat and respiration, light-headedness, jitteriness and frequent urination.1 These symptoms may also develop in those not habitually exposed to caffeine who ingest a moderate dose.

The busy professional who keeps going on 6-8 cups of strong filter coffee per day may be at greater risk than the fitness enthusiast of developing these symptoms. He or she may also experience headache and depressed feelings from caffeine withdrawal at weekends and when on holiday.

Caffeine from tea, coffee, energy drinks/tablets, guarana

Caffeine is ingested from many sources. In many instances people may be unaware of its presence. A standard cup of coffee contains 70-180mg caffeine depending on the strength and method of preparation.1 Instant coffee generally contains less caffeine than coffee prepared from ground beans. Tea contains 20-35mg per cup.1 Chocolate also contains caffeine.

Some of the approved medicines containing caffeine are the diuretic De Witt’s tablets and the sleep inhibitors No Doz and No Doz Plus tablets (all available over-the-counter), and the antimigraine prescription medicines Ergodryl, Migril and Cafergot tablets. These contain up to 100mg of caffeine per dosage unit and the recommended daily dose or dose per migraine attack is up to 600mg. Some soft drinks (Coke, Pepsi and Mountain Dew) and energy drinks (Proton Guarana Blast, V, Stamina, Big Red, Bull Rush and Top Secret) contain caffeine in varying amounts.

Guarana is a dietary supplement which contains caffeine and is quite popular. It is made from a ground extract of the seeds of the plant Poullinia cupana var sorbilis which have a natural caffeine content of around 5%. In some preparations guarana is combined with ginseng. Guarana tablets or capsules are marketed as herbal tonics which are said to increase stamina and endurance and have beneficial effects on the nervous system. A dose unit usually contains the equivalent of about 40mg of active caffeine.

Caffeine withdrawal may cause headache, nausea, depression

Medical practitioners are advised to question patients presenting with possible symptoms of caffeine overdose about their ingestion of caffeine from the less obvious sources such as guarana preparations, dietary supplements used for fitness and energy drinks, as well as from coffee, tea and chocolate.

An individual withdrawing from caffeine because of a chronic toxic overdose may experience symptoms of withdrawal including headache, nausea, nervousness, reduced alertness and depressed mood. These symptoms are most acute during the first 20-48 hours, but they may persist for as long as 7 days2. Discontinuation of caffeine at even a moderate intake can lead to these symptoms. There is also a danger of developing dependence by having that cup of coffee for the headache caused by caffeine withdrawal.

  1. Chou TM, Benowitz NL. Caffeine and coffee: effects on health and cardiovascular disease. Comparative Biochem & Physiol. Part C Pharmacol Toxicol & Endocrinol 1994;109:173-89
  2. Lamarine RJ. Selected health and behavioural effects related to the use of caffeine. J Community Health 1994;19:449-66.


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