Vitamin A should be taken in the form of beta-carotene, which is not considered toxic. The recommended daily allowance (RDA) of vitamin A is 2,670 International Units (IU).

1 mcg of retinol / 6 mcg of beta carotene= 3.33 IU

The FDA has established that in the US an RDA of 5,000 IU for vitamin A but pregnant women should maintain their intake around 8,000 IU. herapeutic doses have ranged as high as 50,000 IU for adults. However, any high dose therapy (more than 25,000 IU for an adult or 10,000 IU for a child) should be closely monitored by a healthcare professional.

Symptoms of overdose include:
* Nausea
* Loss of appetite
* Headache
* Peeling skin
* Hair loss
* Tiredness
* Menstrual irregularity
* Enlarged liver
* Enlarged spleen

Since Vitamin A is stored in the liver, harmful effects can build up gradually. However it is extremely unlikely that any problems would occur unless you are taking 50,000 IU or more a day. Even at teh 50,000 unit level, you would have to continue that dose every day for months to reach a possible toxic level.Some people can tolerate more. 10,000 to 25,000 IU a day should have no problems at all. Serious side effects of vitamin A can be prevented by heading early warning signs. These include fatigue, abdominal discomfort, bone and joint pain, throbbing headache, insomnia, restlessness, sweating, hair loss, brittle nails, constipation, menstrual irregularities and swelling of the ankles.

FYI - Large amounts of carotene may cause your skin to turn orange. This is not a toxic side effect and will go away as carotene is stopped.