We take health supplements because they’re good for us (supposedly), but sometimes too much a good thing is not so good. Especially when it comes to mixing them with other supplements or medications that don’t react well together. Here are some supplement mixtures you should never making.

Fish Oil

Fish oil supplements are a great way to get a dose of omega-3 fatty acids, but they should not be mixed with certain medications. Fish oil can increase the effects of blood pressure lowering drugs which can lower the blood pressure too much. Fish oil can also thin the blood so when they’re taking alongside any other herbs that do the same thing it can reduce the body’s ability to clot blood. If you can, get your omega-3’s from food sources like salmon and flax seed.


Calcium can make certain drugs less effective, such as certain antibiotics and osteoporosis drugs. If you get prescribed tetracycline for any reason be sure and take your calcium at a different time of day so it doesn’t interfere.


The point of taking melatonin is to make you sleepy, but it should not be mixed with anything else that could potentially make you tired like other supplements St. John’s Wort and Valerium. It can also raise the blood pressure, and it can slow the body’s ability to clot blood.

St. John’s Wort

St. John’s Wort is taken by some people to boost their mood, but it does this by increasing the amount of serotonin in the body. If you mix it with an antidepressant or something else that raises the levels of serotonin it can cause heart problems and other serious side effects. It can also make birth control pills less effective, so tell your lady friends if they don’t already know.

Vitamin D

Vitamin D supplements might make cholesterol lowering drugs less effective, and if you mix it with a diuretic it can make the vitamin calcium in the body too high. Too much calcium causes problems for the kidneys.

In addition to not mixing certain supplements, you should also never take more than the dose. Certain supplements and vitamins like vitamin C for example are water soluble, which means that the body will just excrete the excess when it reaches its tipping point. (This is also why too much vitamin C can give you the runs.) Other supplements and vitamins however are fat soluble which means the body will store everything you put in. This is problematic with things like B6 which can cause nerve damage in excess, calcium which can cause depression in excess, and vitamin A which can cause liver problems in excess and sometimes even increase the risk of death.

Always read up on what you’re taking and follow the instructions on the package, if not directly asking your doctor about it. If you are on antibiotics and medications you should always check with a doctor before mixing them with any supplements.