Vitamins and minerals are cofactors in physiological processes in the body; i.e., in building muscle and burning fat, to name just two. All physiological processes in the body are “rate limiting.” In other words, these processes stop when a required vitamin or mineral is no longer available.
But here’s the thing. There are two different types of vitamins; water soluble and fat soluble. The body has the ability to store fat soluble vitamins for later use. But with water soluble vitamins, the body takes what it needs AT THAT PRECISE TIME and excretes the rest. The answer to your problem is not taking your multi-vitamin 3 times a day; the answer is to to take that one pill and divide it into 3 pieces. Your body would then be given 3 opportunities to utilize the water-soluble vitamins it needs, instead of just one opportunity.
Actually, I’m not really recommending that you cut your one-a-day into 3 pieces. Just make sure you’re purchasing a brand that requires you to take their multi a MINIMUM of 2 times per day, with 3 times being better.
I take a multi that instructs you to take 3 pills 3 times per day. And they are horse pills with 67 different ingredients! When I am eating 6 meals a day, I will take 2 multis at my 3 largest/larger meals and 1 multi at my 3 smaller meals.
And yes, to specifically answer your question, 10,000 IU of Vitamin A is considered to be the safe daily upper limit. Taking 30,000 IU per day is not recommended, except in special circumstances.
The “special circumstance” is that 50,000 IU of Vitamin A is sometimes recommended when someone is suffering from a cold or flu. For short periods of time only, though.