Glutamine

amino acid

Take on an empty stomach

What is it

Glutamine is a conditionally essential amino acid that is the most abundant free amino acid in human blood and skeletal muscle. The body normally makes enough on its own, but demand can outstrip supply during severe illness, major surgery, prolonged endurance exercise, or trauma.

How it works

Glutamine serves three jobs the body can't easily shortcut. It is a primary fuel for rapidly dividing cells, especially the enterocytes that line the small intestine and the lymphocytes that drive immune responses. It carries nitrogen between tissues, helping the body recycle amino groups without producing toxic levels of ammonia. And it is a precursor to glutathione, the cell's main internal antioxidant. In the gut, glutamine helps maintain the integrity of the intestinal barrier by feeding the cells that form the tight junctions between them. After heavy training or surgery, plasma glutamine drops while demand from immune cells and the gut spikes, which is the basis for most supplemental use cases. In healthy, well-fed people, the liver and skeletal muscle synthesize ample glutamine from glutamate and ammonia, so additional intake usually has modest effects.

Evidence for 5 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Critical illness and burn recovery

Grade B

Good evidence

Multiple trials in burn and ICU patients have shown that enteral or parenteral glutamine reduces hospital infections and may shorten length of stay. The REDOXS trial in 2013 complicated the picture by finding harm with high-dose IV glutamine in multi-organ failure patients, so current critical-care guidelines distinguish between stable catabolic patients (likely benefit) and those in shock (avoid).

Gut barrier support after illness or stress

Grade C

Moderate evidence

Glutamine is the preferred fuel of intestinal epithelial cells, and supplementation has been studied for short bowel syndrome, post-chemotherapy mucositis, and intestinal permeability in critical illness. Results are most consistent in catabolic patients (trauma, burns, post-surgical), where 20 to 30 grams per day has reduced infection rates and improved gut barrier markers. Evidence in healthy adults with everyday digestive complaints is weaker.

Chemotherapy-related mucositis

Grade C

Moderate evidence

Oral glutamine swish-and-swallow protocols (typically 10 grams three times per day) have shown reduced severity of oral mucositis in some trials of patients receiving 5-fluorouracil-based chemotherapy or radiation. Results are mixed and protocols vary, but the safety profile makes it a low-risk add-on under oncology supervision.

Wound healing

Grade C

Moderate evidence

Glutamine supports collagen synthesis and immune function at wound sites. Studies in surgical and burn patients have shown faster wound closure with supplementation, though most evidence comes from combination amino acid formulas rather than glutamine alone.

Post-exercise recovery and immune support

Grade D

Mixed evidence

Heavy endurance exercise transiently lowers plasma glutamine, and the so-called 'open window' hypothesis suggested that supplementation could blunt post-exercise immunosuppression. Controlled trials in recreational athletes have generally not shown meaningful reductions in upper respiratory infection rates or improvements in performance metrics.

2 commercial forms

L-glutamine (free form)

Standard supplemental form. Stable in dry powder; degrades in solution over hours.

The most common and least expensive form, available as a tasteless powder or capsule. Mix into water and drink promptly because glutamine slowly hydrolyzes to ammonia and glutamate in solution.

Glutamine peptides (e.g., alanyl-glutamine)

More stable in solution and slightly better absorbed in clinical settings.

Used in parenteral nutrition and some sports drinks because the dipeptide form survives aqueous storage longer than free glutamine. For oral home use the cost premium rarely justifies the modest advantage.

Dosage

There is no RDA for glutamine because it is non-essential in healthy adults. Typical supplemental doses range from 5 to 10 grams once or twice daily for general use, and clinical protocols in burn or critical-care settings have used 20 to 30 grams per day under medical supervision. Athletes commonly take 5 grams post-workout. The body produces roughly 50 to 80 grams per day endogenously, which dwarfs most supplement doses.

When and how to take it

Glutamine is typically taken on an empty stomach to maximize absorption, although it can be taken with food without major loss of effect. Common timing is first thing in the morning, between meals, or immediately after exercise when muscle and immune demand are elevated. For gut health protocols, splitting the dose into 5 grams two to three times per day in a glass of water keeps glutamine available throughout the day. There is no strong reason to avoid it later in the evening, though some people prefer to take it earlier because the energizing effect on the gut and immune system is mild but real.

Food sources

Food	Amount	%DV
Beef	~1.2 g per 3 oz	—
Eggs	~0.6 g per large egg	—
Tofu	~0.6 g per half cup	—
Cottage cheese	~1.7 g per cup	—
Cabbage	~0.3 g per cup	—
Spinach	~0.3 g per cup raw	—
Lentils	~0.6 g per cup cooked	—

Safety

Glutamine has a well-tolerated safety profile at typical supplemental doses. Reported side effects are uncommon and usually mild: bloating, gas, or nausea, often resolved by splitting the dose or taking with water. No formal Tolerable Upper Intake Level has been established. Doses up to 30 grams per day have been used short-term in clinical research without significant adverse events. People with liver or kidney disease should be cautious, because glutamine metabolism produces ammonia and glutamate that compromised organs may not clear efficiently. Anyone with a history of seizures, hepatic encephalopathy, or Reye's syndrome should avoid supplementation without medical guidance. Long-term high-dose use has not been well studied.

Who should be cautious

Avoid or use only under medical supervision if you have cirrhosis, kidney failure, a seizure disorder, bipolar disorder with mania, or a history of monosodium glutamate sensitivity. Pregnant and breastfeeding women should not exceed dietary intake without a clinician's input because safety data are limited. People on a low-protein medical diet for hepatic encephalopathy should specifically avoid supplemental glutamine.

Interactions

Glutamine can theoretically interfere with anti-seizure medications such as phenobarbital, phenytoin, and carbamazepine by being converted to glutamate, an excitatory neurotransmitter. It may also reduce the effectiveness of lactulose, which is used to lower ammonia levels in liver disease, because glutamine metabolism generates ammonia. Some chemotherapy regimens use glutamine to reduce mucositis, but timing relative to treatment should be coordinated with an oncologist.

Frequently asked questions

Do I need glutamine if I eat plenty of protein?⌄

Probably not. A diet with 0.8 to 1.6 grams of protein per kilogram of body weight typically supplies 3 to 6 grams of glutamine per day from food, plus your body makes 50 to 80 grams on its own. Supplementation is most useful in catabolic states (illness, surgery, severe training) where demand temporarily exceeds supply.

Does glutamine help build muscle?⌄

On its own, no. Trials testing glutamine for muscle hypertrophy or strength have been largely negative in healthy lifters with adequate protein. Leucine and total protein intake are far more important for muscle growth.

Will glutamine fix leaky gut?⌄

Glutamine genuinely fuels intestinal cells and supports tight junctions, and it shows benefit in measurable intestinal permeability after burns or surgery. 'Leaky gut syndrome' as marketed to healthy adults is not a recognized diagnosis, and evidence for symptom relief in IBS or other functional gut disorders is mixed.

Can I take glutamine on an empty stomach?⌄

Yes, and that is the most common protocol. Empty-stomach dosing slightly speeds absorption, which is why many users take 5 grams first thing in the morning or post-workout.

Is glutamine safe long-term?⌄

Short and medium-term studies up to several months at 5 to 30 grams per day have shown few side effects in healthy adults. Long-term safety beyond a year has not been formally studied. People with liver or kidney disease should not take it without supervision.

References

Wikidata: Glutamine — Wikidata link
PubChem: Glutamine (CID 5961) — PubChem link
ChEBI: Glutamine (CHEBI:28300) — ChEBI link

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Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you're pregnant, breastfeeding, on medications, or managing a chronic condition.