SupplementsAmino AcidsArginine
Arginine
L-arginine
The amino acid your body turns into nitric oxide to open up blood vessels, though your gut takes most of it first.
- Builds up
- About 2 weeks
- In your body
- 1-hour peak
- Per 1 capsule
- 500 mg
- 30-day supply
- $7.43One capsule a day, plus packing and delivery
What is arginine?
L-arginine is an amino acid, one of the building blocks of protein. You get it from red meat, poultry, fish and dairy, and your body can make some of its own from another amino acid called citrulline.
Its best-known job is as the raw material for nitric oxide, a gas your body uses to tell blood vessels to open wider. It also nudges your body to release growth hormone and insulin.
Ours comes in 500 mg capsules, and L-arginine is the only active ingredient.
What it does
- Blood flowSupports healthy circulation as the raw material for nitric oxide.
- Blood pressureHelps maintain blood pressure already in the healthy range.
- ProteinA building block for the proteins your body makes.
- Hormone signalsPlays a part in the normal release of growth hormone and insulin.
These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure or prevent any disease.
What people take it for
Some evidenceBlood pressureStudies found a drop of about 5 to 6 points in the top number, at amounts far above one capsule.
Some evidenceSexual functionIn studies of men with mild to moderate erection problems, it did better than a dummy pill, at 1.5 to 5 g a day.
Early daysExerciseIt's a staple of pre-workout drinks, yet in a head-to-head study citrulline helped and arginine didn't.
How long it takes
It doesn't really pile up. At large daily amounts, blood levels sat about 40% above normal by week 2 and simply held there through week 12.
- 1 hourThe highest level in your blood after a large amount
- 2 weeksBlood levels have settled a little higher, at large daily amounts
- 4 weeks or moreHow long many of the blood pressure studies ran
How long it stays in your body
After a large amount, it's highest in your blood at about 1 hour and then falls away slowly. The researchers couldn't pin down a half-life, and levels still hadn't quite settled back 8 hours later.
What's in a capsule
One capsule holds 500 mg. Blood pressure studies used 4 to 24 g a day and erection studies used 1.5 to 5 g a day, so one capsule holds less than any of them.
Why most of it never arrives
Your gut gets to arginine first. An enzyme in your intestine breaks a lot of it down before it ever reaches your blood. In one study, only about 20% of a 10 g amount made it through.
That's why so many people now look at citrulline, its close cousin, and how the two compare is in the full guide.
There's also one caution that matters more than any other here. In a trial of people recovering from a heart attack, arginine didn't help their arteries or their heart's pumping, and 6 of the people taking it died, compared with none of those on a dummy pill. The trial was stopped early. So if you've recently had a heart attack, this one isn't for you.
What it interacts with
- Blood pressure medicinesArginine can lower blood pressure too, so the two together could take it too low.
- Sildenafil (Viagra)Both lower blood pressure. Most people seem fine together, but check first.
- Diabetes medicinesIt might lower blood sugar further, so keep a closer eye on your numbers.
- Blood thinners and antiplatelet medicinesIt might slow clotting, which could make bruising and bleeding more likely.
- Potassium-sparing water pillsArginine might raise potassium, and these do too.
- TestosteroneArginine might raise testosterone a little. It's not clear this matters much.
Goes well with
Side effects
- Stomach pain, bloating and diarrhea, mostly with large single amounts. Single amounts of 3 to 6 g rarely caused trouble in studies.
- Low blood pressure, especially if yours already runs low.
- In erection studies, about 8 in 100 people reported a side effect, and none were serious.
Check first if
- Recent heart attack: don't use it. It may raise the risk of death, especially in older people.
- Kidney disease: it has caused high potassium in people with kidney disease, sometimes with a dangerous heart rhythm. Ask your doctor first.
- Surgery: stop at least 2 weeks before a planned operation, because it might interfere with blood pressure control.
- Pregnancy or breastfeeding: long-term safety isn't known, so talk to your doctor first.
- GAMT deficiency, a rare inherited condition: avoid it.
The blood tests that go with it
- PotassiumArginine has raised potassium in people with kidney disease.
- eGFRShows how well your kidneys filter, which is worth knowing before you start.
- Fasting glucoseArginine might lower blood sugar.
- Fasting insulinArginine prompts your body to release insulin.
- Growth hormoneArginine prompts its release too, so mention it if yours is being tested.
- Total testosteroneArginine might raise it a little, though it's not clear by how much.
Work it out
Supplementation
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These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease.
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A page can only tell you about Arginine. The app tells you about you: whether it fits, when to take it, and whether it's working.
- Checked against your blood work and everything you already take
- On your daily timeline, around your sleep, training and meals
- Followed over time, so you can see what moved
ArginineOPEN 09:00Arginine against your blood work, your sleep and what you already take.
AIYour potassium and eGFR both look fine on your last blood test. Worth a word with your doctor about arginine, since you take a blood pressure medicine?
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Questions
What is L-arginine good for?
People mostly take it for blood flow, blood pressure and sexual function in men. Those are the areas with the most research behind them.
How long does L-arginine take to work?
It reaches your blood within about an hour, but you won't feel that. Many blood pressure studies ran for 4 weeks or longer, at much larger amounts than one capsule.
What are the side effects of L-arginine?
Mostly stomach pain, bloating and diarrhea, plus low blood pressure in some people. Large single amounts are more likely to cause stomach trouble.
Who should not take L-arginine?
Anyone who has recently had a heart attack, and anyone with GAMT deficiency. If you have kidney disease, take blood pressure or blood sugar medicines, use blood thinners, or are pregnant or breastfeeding, talk to your doctor first.
Can I take L-arginine every day?
Studies have given it daily for up to 18 months. Long-term safety is less well known than short-term safety, so check in with your doctor if you plan to stay on it.
What is the half-life of L-arginine?
There's no clean figure. In the main study the researchers couldn't work one out. It peaks at about 1 hour and falls slowly over the next 8 hours or so.
Does L-arginine interact with medicines?
Yes, with several, including blood pressure medicines, sildenafil, diabetes medicines, blood thinners and some water pills. The list above is a good one to show your pharmacist.
Does arginine trigger cold sores?
Nobody's sure. Lab studies found the cold sore virus grows better when arginine outweighs lysine, but we didn't find good evidence that capsules trigger outbreaks in people. If you get them often, keep an eye on it.
Which foods contain arginine?
Red meat, poultry, fish and dairy. A normal diet gives you a steady supply without any capsule.
Sources
- MedlinePlus. L-arginine (archived copy; the natural medicines section has since been retired).
- Tangphao O et al. Pharmacokinetics of intravenous and oral L-arginine in normal volunteers. Br J Clin Pharmacol, 1999.
- Tangphao O et al. Pharmacokinetics of L-arginine during chronic administration to patients with hypercholesterolaemia. Clin Sci, 1999.
- Dong JY et al. Effect of oral L-arginine supplementation on blood pressure: a meta-analysis. Am Heart J, 2011.
- Shiraseb F et al. Effect of l-arginine supplementation on blood pressure in adults. Adv Nutr, 2022.
- Rhim HC et al. The potential role of arginine supplements on erectile dysfunction. J Sex Med, 2019.
- Schulman SP et al. L-arginine therapy in acute myocardial infarction (VINTAGE MI). JAMA, 2006.
- Schwedhelm E et al. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine. Br J Clin Pharmacol, 2008.
- Bailey SJ et al. l-Citrulline supplementation improves O2 uptake kinetics and high-intensity exercise performance in humans. J Appl Physiol, 2015.
- Grimble GK. Adverse gastrointestinal effects of arginine and related amino acids. J Nutr, 2007.
- Griffith RS et al. A multicentered study of lysine therapy in Herpes simplex infection. Dermatologica, 1978.
Written by LifeFrom from these sources, and not yet reviewed by a clinician. Talk to your doctor before starting a supplement.
