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Amino acids & derivatives

L-histidine

L-histidine

L-histidine is an essential amino acid sold as L-histidine HCl or base. It participates in normal protein metabolism and histamine biology, but that does not establish a general memory or focus effect. Human research is limited to high-fatigue groups: the 2026 single-dose RCT did not show superiority in the all-participants analysis, and its exploratory subgroup findings need replication. Compare HCl versus base, the labelled amount, and serving size.

Mental EnergyFatigue ResistanceCellular SupportNeurotransmitter PrecursorFood DerivedWater SolubleClinical Research
Updated August 2026/5 min read/7 citations
Reviewed by the NootropicsIndex editorial team.Method: prioritize cited human research and official safety or regulatory sources; compare retailer-listed prices without endorsing products.Affiliate disclosure
01

What is it?

What L-histidine is

3

L-histidine is a nutritionally essential amino acid that appears in protein foods. For product comparison, the exact salt/base label, formulation, and serving size matter more than the generic amino-acid name.

High-fatigue evidence is population-specific5
Small human studies have evaluated L-histidine in high-fatigue groups. This population-specific research does not establish a general nootropic benefit.
The 2026 result needs restraint6
In the 2026 single-dose RCT, the all-participants analysis did not show superiority over placebo. An exploratory high-fatigue subgroup had mood findings; that subgroup result needs replication.
No broad nootropic claim5
No reliable L-histidine evidence supports broad memory, focus, calm, or general cognitive claims.
02

Names, aliases and forms

Common NamesL-histidine; Histidine
Chemical NameL-2-amino-3-(1H-imidazol-4-yl)propanoic acid
AbbreviationHis
Salt FormL-histidine HCl
Freebase FormL-histidine base
Pubchem Cid6274
03

Mechanisms of action

Histamine and carnosine pathways explain the interest

4

Histidine is involved in histamine and histidine-containing dipeptides such as carnosine. That biology is relevant, but it should not be simplified into a promise of better memory, focus or mood.

04

Potential effects and evidence map

Human L-histidine evidence is limited and population-specific. A 2026 single-dose RCT did not show superiority over placebo in its all-participants analysis; exploratory high-fatigue subgroup findings need replication. This is not evidence for broad nootropic, memory, or routine focus claims.

Effect domainMagnitudeGrade
Mental energy / wakefulness6
UnknownConfidence: Low

High-fatigue research is limited: the 2026 all-participants analysis was not superior to placebo, while exploratory subgroup findings need replication.

Note Do not generalize the high-fatigue research to routine energy or productivity use.

1/5
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05

Typical dosages and timing

Form and serving2HCl / base

In the 1 August 2026 catalog snapshot, L-histidine products include HCl and base forms in powder and capsule formats. Compare the exact chemical form, labelled amount, and serving size; the cited studies do not establish a transferable routine dose.

06

Timing & effect horizon

Effect horizonUnknown
Unknown
Study design is not routine timing6

The 2026 trial assessed a single dose. This is a study design, not an established onset, duration, schedule, or cycle for ordinary use.

07

Safety, side effects and risk profile

Histamine biology is not a clinical response claim3
Histidine is a precursor of histamine. This metabolic role does not establish that L-histidine supplements cause a specific response in people with histamine-related concerns; product-specific clinical safety data are limited.
Liver-disease context needs individual review4
A 2020 review advised against histidine supplementation in liver disease based on discussed biochemical and experimental concerns. This does not establish an equivalent kidney-risk conclusion.
Evidence uncertainty6
Confidence: High

The main practical risk is overstating limited, population-specific findings as a broad nootropic benefit.

Note The 2026 RCT did not show superiority in all participants; subgroup findings were exploratory.

1/5
C
08

Interactions and cautions

Interaction evidence3

The cited sources do not establish specific L-histidine drug interactions. Individual prescription or medically supervised nutrition contexts need professional review rather than a generic stack rule.

09

Legal and regulatory status

United States - FDA, 20267

As of 2026, FDA does not approve dietary supplements for safety or effectiveness before they are marketed. This U.S. regulatory context does not determine legal status in other markets.

10

Practical buying and quality notes

  • The 1 August 2026 snapshot contains 31 active listings from 2 vendors: 27 powders and 4 capsules. Listing titles signal 12 HCl and 13 base products. Compare the exact form, stated amount, serving size, and whether the label reports L-histidine amount or salt weight.2
  • Compare powder prices per gram only within the same chemical form: HCl to HCl or base to base. Do not infer equivalence across salt forms from package grams. For capsules, compare stated L-histidine amount per serving rather than capsule count alone. Exclude the one zero-quantity row and three zero-normalized-price rows from price, availability, and per-dose comparisons.2
11

FAQ

Is L-histidine the same as histidine?

1

For supplement comparison, the useful distinction is usually L-histidine versus salt/form labels such as L-histidine HCl or L-histidine base. Generic histidine wording is less precise.

What L-histidine dose or cycle is established?

5

No transferable consumer dose, onset, duration, or cycle is established by the cited research. Compare product form and label serving rather than borrowing a study protocol.

Does L-histidine improve focus?

6

No reliable evidence supports a broad focus benefit. The small high-fatigue studies do not establish an ordinary healthy-user focus result.

Who should not extrapolate general product copy?

4

The cited review raises a liver-disease caution. Reliable product-specific interaction and pregnancy/lactation data were not identified in the cited sources, so general adult product copy should not be extrapolated to those contexts.

12

References

  1. PubChem. L-Histidine (CID 6274).
  2. NootropicsIndex product catalog snapshot for L-histidine, queried 1 August 2026.
  3. Kessler AT, Raja A. Biochemistry, Histidine. StatPearls. Updated 2023.
  4. Holecek M. Histidine in Health and Disease: Metabolism, Physiological Importance, and Use as a Supplement. Nutrients. 2020.
  5. Sasahara I, Fujimura N, Nozawa Y, Furuhata Y, Sato H. Histidine and mental fatigue/cognitive performance in high-fatigue subjects. Physiol Behav. 2015.
  6. Shimomasuda M, Fujiyoshi H, Kajiyama Y, et al. Single-dose L-histidine, mental fatigue and vigor in high-fatigue participants. Sci Rep. 2026.
  7. U.S. Food and Drug Administration. Information for Consumers on Using Dietary Supplements.
Note

This page is informational and summarizes available evidence. It is not medical advice, a recommendation, or a substitute for guidance from a qualified clinician.