Many people ask themselves: “How much fish oil should I take?”. Unfortunately the answer isn't as easy as “X milligrams per day”. Basically fish oil is beneficial for one's health because it contains omega-3 acids, so the properly stated question you should have asked is “How much omega-3 acids should I take?”. As usual with supplements-related issues the answer depends on your current health.
Omega-3 dosage for healthy people
You can find different amounts throughout the Internet so let's stick to the AHA (American Heart Association) which states (take note that EPA and DHA are omega-3 acids):
Evidence from prospective secondary prevention studies suggests that taking EPA+DHA ranging from 0.5 to 1.8 grams per day (either as fatty fish or supplements) significantly reduces deaths from heart disease and all causes.
Omega-3 dosage for people with medical conditions
There are numerous medical conditions under which omega-3 acids supplementation is worth using. Some of them can be found on Wikipedia. If you have some medical condition the most important thing for you is to consult the amount of supplementation with your doctor. Doing this on your own might end not as well as you may think. It's far more profitable to consult an expert than to take the matter into your own hands (at least in this case).
Look for omega-3 acids quantity
Omega-3 acids are only a part of every fish oil supplement so it's critical for you to check the quantity of them in a supplement you are buying. If it's low (like 300mg per 1000mg) you might look for another fish oil supplement. The bottom line is that you shouldn't buy the cheapest available product but find something that meets your needs.
Count daily capsules intake
In this part I assume that you're prot amounts throughout the%2-3 acids using supplements. If you try to provide the proper quantity of omega-3 acids consuming only fish you should rethink that idea. Don't get me wrong – fish are great for one's health but only in reasonable amounts because they contain some toxins which most (check you product!) fish oil supplements doesn't contain. Combining eating fish 2-3 times a week with some fish oil supplements would be great.
So, the math behind this is easy: if you need 1000mg of omega-3 and your supplement contains 300mg in every capsule you will need to consume at least 3 capsules per day. However, if your supplement contains 500mg in every capsule you will only need 2 capsules per day. This means you should choose your product appropriately so you can easily provide yourself with adequate quantity of omega-3 acids on daily basis.
In the end you should remember that it's omega-3 acids that really matters, not just any fish oil. The omega-3 acids dosage depends on your health conditions. If you're just starting with omega-3 supplements you should increase the dosage gradually until you reach your needed quantity. If you have any medical conditions you should consult your doctor before increasing (or decreasing) omega-3 dosage.