The dose is 1500mg but divided into three doses. So get 500mg tablets, and take 1 x 3 times daily.
I generally only recommend this cleanse to people who tend to suffer from gall stones. You don't need to have stones to do it, but as a general cleanse it can be a tad depleting. But yes, it's cheap and effective nonetheless.
I have already written this procedure for someone else, and I've done it myself. I'll just copy and paste it here:
You will need:
1) 500mg Malic Acid in tablet form (find at any health food store) - Douglas Labs is the best brand, but any will do, and if you can get one that has a small amount of magnesium in it, then even better.
2) Epsom salt (magnesium sulfate)
3) Good quality olive oil.
4) Whole grapefruits or lemons (you'll need 1/2 cup of the fresh juice)
5) Pure water
* This cleanse will take a total of 7 days, and on the 7th day you should be at home because you will need the toilet often. Warn others you live with.
** If you don't have 7 days, you can shorten it to 6 days.
For the duration of the cleanse, do not consume any dairy, meat, or fried foods. Do eat plenty of fruits, vegetables, and whole grains.
For the first 6 days, take 1 tablet (500mg) of malic acid three times a day with meals. That's a total of 1500mg of malic acid per day.
In the afternoon or evening of the 6th day, you will take your final dose of malic acid. Do not eat another meal after this point. Here is the schedule for the rest of day 6:
4-5pm: ingest one tablespoon of epsom salt dissolved in water.
2 hours later (7pm): ingest another tablespoon of epsom salt in water.
2 hours after that (9pm): mix one half cup olive oil with one half cup grapefruit juice. Ingest.
Go to bed not long after. Everything you've done will take 8-12 hours to take effect.
Morning of day 7:
Without eating breakfast, ingest another tablespoon of epsom salt in water.
2 hours later: ingest another tablespoon of epsom salt in water. This will be your 4th and final dosage.
Then wait.
After your first major bowel movement, you are free to eat.
Explanation of what's happening:
The malic acid releases any old bile in the liver and into the gallbladder, and any build up along with it. It also softens stones. Epsom salt opens the bile duct so that contents may escape into the small intestine. The oil you ingest is a fat and will trigger your gall bladder to contract to release all its contents, including stones. Since the duct will be fully open, you can expect some explosive bowel movements on day 7 so stay home all day. You'll notice in the toilet that there are green and yellow balls that may even look like sand. Those are stones and various deposits.
Once day 7 is done, congratulations, you have just flushed your liver and gallbladder. You should notice improvements in digestion, bowel movements, and general well being. Anyone who has or suspects that they have gallstones can benefit greatly from this simple cleanse, as it will prevent complications down the road. You don't need to have stones though to do this.