Any drug or supplement can cause side effects. L-arginine is no exception.
L-arginine affects the way your body handles waste, so it can have adverse effects on the organs involved in waste disposal. Some liver and kidney problems can be exacerbated by L-arginine. Using L-arginine can also lead to problems of potassium balance and dehydration, as well as stomach cramps, nausea and other digestive discomfort [source: MedlinePlus].
There can also be some circulatory side effects associated with L-arginine. People recovering from heart attacks shouldn't take it [source: Drugs.com]. There's a possibility that, because it dilates blood vessels, it increases the risk of excessive bleeding. Hemophiliacs and people on blood thinners should probably steer clear. So should people who are taking gingko biloba, another herbal supplement that can heighten the risk of bleeding [source: MedlinePlus]. Sometimes L-arginine can make problems of low blood pressure more severe. And people with sickle cell disease may find that their symptoms get worse [source: Mayo Clinic].
You'd think that, because L-arginine production can be hindered by dialysis, it'd be a natural choice to recommend L-arginine supplements to diabetics. However, there's some evidence that the amino acid actually raises blood sugar [source: Mayo Clinic]. Once again, the workings of chemicals in the body are incredibly complicated.
One of the most severe potential side effects of L-arginine is anaphylaxis [source: Mayo Clinic]. That's a very severe allergic reaction that can result in shock and potentially even death. In an anaphylactic reaction, you may experience sudden chills, sweating, tremors, hives, vomiting, and diarrhea, shortness of breath and light-headedness or fainting -- all at once. It's not pleasant. If you have any allergies, don't take L-arginine before being tested for an allergy to it.
One final note: Beware of herbal supplements promising L-arginine. Herbal supplements are not subject to the same FDA regulations as prescription pharmaceuticals are. Among other things, this means that in two identical-looking pills from the same bottle, the dosage may vary. You may not always be able to predict the effects of the supplement -- even from day to day.
On the next page, we'll take a look at the ways L-arginine might be able to aid in human growth.