In the excitement to learn all about agmatine’s muscle building benefits, however, the side effects conversation is usually tabled and never revisited.
Direct Agmatine Side Effects
In a clinical study, agmatine was given to subjects in escalating dosages starting at 1.335 g/day for 10 days and culminating with 3.560 g/day for 21 days.
Aside from three participants in the highest dose cohort experiencing mild-to-moderate diarrhea and mild nausea during treatment, no other events were observed.
According to this study, there doesn’t appear to be any other side effects from taking agmatine apart from gastrointestinal issues.
Indirect Agmatine Side Effects
Additional agmatine side effects can be considered a consequence from boosting nitric oxide levels. When using agmatine or any other vasodilator it’s important to be aware of these side effects:
- Reduced dopamine levels: Dopamine is a chemical messenger which plays an important role in mood, cognitive ability, and sleep. Nitric oxide, and therefore agmatine, has an inhibitory effect on dopamine transporters, and significantly reduces uptake.
- Blood pressure changes: Nitric oxide widens blood vessels and reduces blood pressure. While this may be desirable, if you have hypotension or experience a dramatic decrease in blood pressure this can cause dizziness, fainting, and might be life threating in some cases.
- Blood sugar changes: Changes in blood sugar from agmatine supplements is mainly a concern for diabetics, who must carefully monitor glucose levels.
Alleged Agmatine Side Effects
In addition to gastrointestinal issues, some users on the Bodybuiding.com forum have commented they experienced headaches when taking agmatine. Keep in mind this is an anecdotal side effect and not based on research.
Should You Still Use Agmatine?
Agmatine is relatively safe and effective. Even the gastrointestinal issues were only experienced by a few subjects taking an extremely large dose. Always check with a doctor if you are concerned with any issues arising from increased nitric oxide levels.
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-  “Low Blood Pressure (hypotension).” Mayo Clinic.
-  Kingwell at al. “Nitric Oxide Synthase Inhibition Reduces Glucose Uptake During Exercise in Individuals With Type 2 Diabetes More Than in Control Subjects.” Diabetes. August 2002 vol. 51 no. 8 2572-2580
-  “Hemavol = headache! – Bodybuilding.com Forums.” Bodybuilding.com Forums – Bodybuilding And Fitness Board. Bodybuilding.com.