I've been researching this a little here. I'm finding conflicting reports. Seems like when juicing was big, people were OD'ing on Vit A. There was even something on the Snopes (urban legend) site about it -- that I didn't read though. Here's a tidbit of info:
Question: Is it possible to overdose on vitamin A from foods?
Answer: Vitamin A is an important part of a healthy diet. We get it from foods containing the vitamin itself or beta-carotene, which the body uses to make vitamin A as needed. Because the body regulates how much beta-carotene turns into vitamin A, it is difficult to eat too much beta-carotene. But it is possible to ingest too much vitamin A.
Vitamin A and beta-carotene are found in orange fruits and vegetables like carrots, butternut squash, pumpkins, mangoes, and dark green vegetables such as spinach and broccoli. Organ meats (liver and kidney) contain very high amounts of vitamin A.
Overdosing on vitamin A can cause headache, irritability, itchiness, and skin rashes-- even liver damage. Severe symptoms can develop in healthy people if they consume more than 500,000 IU (International Units) all at once, but chronic toxicity with equally dangerous symptoms can be caused if a person takes more than 25,000 IU daily. Also, taking more than 15,000 IU during early pregnancy can cause birth defects, so pregnant women and people with kidney disorders should not take vitamin A or beta-carotene supplements unless directed by a medical doctor.
Studies of people who get lots of vitamin A and beta-carotene from fruits and vegetables tend to have lower rates of heart disease and cancer. But taking these nutrients in pill from (either alone or in a multivitamin) does not appear to have the same benefit.
So while it's unlikely that anyone could overdose on vitamin A or beta-carotene through foods alone, it is possible if you eat organ meats or take supplements high in Vitamin A. Discuss your concerns with your doctor or a dietitian/nutritionist.
(Polar bear liver is toxic for that reason, though. Don't ever eat one.)
My research on Vitamin A. Essentially you get it from dairy and dark leafy vegetables (carrot tops are dark leafy). The plant version (beta carotine) is the good version and it's really hard to overdose on that. The animal version (retinol) can be overdosed on but it would take a lot.
On the other hand, once you start to turn orange you may want to cut down on the carrots.