Comparison
L-Theanine vs Metformin
Side-by-side of L-Theanine and Metformin. Every row below is pulled from the compound schema and will update as our data grows. For deeper reads, follow through to each compound page.
L-Theanine
L-theanine is a non-protein amino acid found in tea leaves. The most-replicated nootropic; pairs with caffeine at 1:1 (100-200 mg each) for acute focus.
Metformin
Metformin for longevity: biguanide mechanism of action, TAME trial status, anti-aging dosage, weight loss data, life extension evidence in non-diabetics.
Effects at a glance
L-Theanine
- •Non-protein amino acid in tea; the most-replicated nootropic in the human RCT literature
- •Caffeine + theanine at 1:1 (100-200 mg each) is the gold-standard acute focus stack
- •Solo doses of 200-400 mg reduce subjective stress and improve sleep quality
- •Increases alpha-wave EEG activity within 30-45 minutes of 200 mg oral dose
- •Crosses blood-brain barrier; bioavailability high, half-life 60-90 minutes
- •Clean safety record; minimal interactions at supplement doses
Metformin
- •Reduces HbA1c by ~1.0 to 1.5 percentage points in type 2 diabetes; first-line agent in major guidelines
- •DPP trial: 31% reduction in T2DM incidence in adults with prediabetes over 2.8 years
- •Suppresses hepatic gluconeogenesis via AMPK activation and complex I inhibition
- •Long-term use depletes B12; annual monitoring recommended after year 2
- •Lifespan extension in non-diabetic humans is not established; TAME trial pending
- •MASTERS trial reported blunted resistance-training hypertrophy in older adults
Side-by-side
| Attribute | L-Theanine | Metformin |
|---|---|---|
| Category | supplement | pharmaceutical |
| Also known as | theanine, gamma-glutamylethylamide | Glucophage, Fortamet, Glumetza, dimethylbiguanide |
| Half-life (hr) ↗ | 1.5 | 6 |
| Typical dose (mg) ↗ | 200 | 1500 |
| Dosing frequency | as needed (with caffeine) or daily | 1 to 3 times daily with meals; XR once daily |
| Routes | oral | oral |
| Onset (hr) | 0.5 | 1 |
| Peak (hr) | 1 | 2.5 |
| Molecular weight | 174.2 | 129.16 |
| Molecular formula | C7H14N2O3 | C4H11N5 |
| Mechanism | Crosses BBB; modulates GABA/dopamine/serotonin (modest); increases alpha-wave EEG activity; dampens stress-induced sympathetic response without sedation. | Suppresses hepatic gluconeogenesis primarily via AMPK activation and complex I inhibition; modestly improves peripheral insulin sensitivity and shifts gut microbiome composition. |
| Legal status | OTC dietary supplement | Prescription only (FDA approved for type 2 diabetes 1994) |
| WADA status | allowed | allowed |
| DEA / Rx | OTC supplement | Rx only (not a controlled substance) |
| Pregnancy | Insufficient supplement-dose data; tea-source intake safe | Category B; used in gestational diabetes and PCOS per current guidance |
| CAS | 3081-61-6 | 657-24-9 |
| PubChem CID | 439378 | 4091 |
| Wikidata | Q909931 | Q19484 |
Safety profile
L-Theanine
Common side effects
- mild GI upset (rare)
- headache (rare)
Contraindications
- pregnancy / lactation (insufficient data at supplement doses)
- concurrent strong GABAergics without caution
Interactions
- caffeine: synergistic for acute focus; dampens jitter without blunting alertness(minor)
- benzodiazepines / alcohol: potential additive sedation(minor)
Metformin
Common side effects
- nausea
- diarrhea
- abdominal discomfort
- metallic taste
- decreased appetite
- B12 depletion (long-term)
Contraindications
- eGFR below 30 mL/min/1.73m2
- acute or chronic metabolic acidosis
- severe hepatic impairment
- acute heart failure
- iodinated contrast within 48 hours
Interactions
- iodinated contrast media: renal injury risk; hold 48 hours peri-imaging(major)
- alcohol (heavy use): elevated lactic acidosis risk(major)
- cimetidine: raises metformin plasma levels via OCT2 inhibition(moderate)
- insulin and sulfonylureas: additive hypoglycemia risk in combination(moderate)
- dolutegravir: raises metformin exposure via OCT2(moderate)
Which Should You Take?
L-Theanine comes out ahead for most readers on the criteria we weight: 3 catalogued goals, OTC dietary supplement, oral dosing, with a Tier-A outcome catalogued. Metformin is the right call when one of the conditionals below applies.
- → If your priority is focus or working memory, pick L-Theanine.
- → If your priority is stress and HPA-axis regulation, pick L-Theanine.
- → If your priority is metabolic health and glucose control, pick Metformin.
- → If your priority is healthspan extension, pick Metformin.
Edge case: If you want to avoid prescription-only, L-Theanine is the more accessible choice.
Default choice: L-Theanine. Lower friction to source, a Tier-A evidence outcome catalogued, and broader goal coverage. Reach for Metformin only if your priority sits squarely in the goals it owns above.
This verdict is generated from each compound's schema (goals, legal status, evidence outcomes, dosing route). It updates automatically as our compound data evolves; the deeper read sits on each individual compound page.
Common questions
What is the difference between L-Theanine and Metformin?
L-Theanine and Metformin differ in category (supplement vs pharmaceutical), mechanism, and typical dosing. See the side-by-side table for full details.
Which has a longer half-life, L-Theanine or Metformin?
L-Theanine half-life is 1.5 hours; Metformin half-life is 6 hours.
Can you stack L-Theanine with Metformin?
Stack compatibility depends on mechanism overlap, legal status, and individual response. Check each compound page for specific interactions and contraindications before combining.
Go deeper