L-arginine is likely safe when taken in levels normally found in foods. Side effects sometimes seen include stomach upset, nausea, diarrhea, bloating, lower back pain, restless legs, gout, night sweats, hives, and rash.
If you experience a severe allergic reaction to L-arginine (swelling of face and throat, difficulty breathing), stop using the supplement and seek medical help right away.
If you have any sort of cardiovascular disease, speak with your doctor about using L-arginine, especially if you are using it for more than 6 weeks. In general, you should not take L-arginine beyond 3 to 6 months without consulting a health care provider. If your condition worsens at any time, see your doctor. If you have kidney diseases, are on a low-protein diet, or are trying to increase your physical activity, talk to your doctor before you start.
There have been reports of increased rates of death following a heart attack when L-arginine (3 g of L-arginine 3 times daily for 6 months) is added to standard post-heart-attack medications. If you have recently had a heart attack, do not use L-arginine supplements.
Since L-arginine can be converted to nitric oxide in your body and can add to the blood-lowering effects of nitrate medications (e.g., nitroglycerin), it may cause your blood pressure to drop too low when taken with other blood-pressure-lowering medications, and may increase the risk of dizziness and lightheadedness. Do not take L-arginine with blood-pressure-lowering medications without first speaking with your doctor.
L-arginine may increase the risk of bleeding and therefore should be used with caution by people with bleeding disorders or taking drugs with similar properties (e.g., anticoagulants).
L-arginine may also change blood sugar levels. Individuals with diabetes or taking diabetic medications should use it with care.
L-arginine can make airway swelling worse in people with asthma. If you have asthma, consult with your doctor before you start taking L-arginine.
It is not known how safe L-arginine is for use by pregnant and breast-feeding women. Talk to your doctor before using this supplement if you are pregnant or breast-feeding.
L-arginine can interact with the following medications:
- anticoagulants (e.g., warfarin, heparin)
- diabetic medications
- ginkgo biloba
- medications that lower blood pressure (e.g., nitrates, sildenafil)
- saw palmetto
Before taking any new medications, including natural health products, speak to your physician, pharmacist, or other health care provider. Tell your health care provider about any natural health products you may be taking.