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    Ingredient guide · Ingredient reference

    GLA supplements: oil sources, evidence and label amounts

    Gamma-linolenic acid, or GLA, is an omega-6 fatty acid found in oils such as evening primrose, borage and black currant oil. The total oil amount is not the same as its GLA content, and evidence about one preparation does not establish every claimed use.

    Read the evidence ↓

    Supplement Science Insights Editorial Team

    Published September 23, 2026

    GLA is a component of an oil

    NCCIH identifies evening primrose oil as an omega-6 source containing GLA and lists borage and black currant oils among GLA-containing supplements. A capsule labeled with an oil’s total weight need not contain that weight of GLA. Look for a separate declared GLA amount or concentration. [1][2]

    Keep the condition and formulation attached to the evidence

    NCCIH describes possible rheumatoid-arthritis symptom benefits from GLA oils but emphasizes the small number of studies for each oil. Its current evening-primrose summary finds insufficient evidence to support that oil for health conditions overall. These summaries do not establish a universally effective GLA dose or justify replacing rheumatoid-arthritis care. [2][1]

    Safety follows the whole preparation

    Evening primrose oil can cause abdominal discomfort, nausea or diarrhea, and medicines should be reviewed before use. Those observations are about that oil, not a complete safety assessment of borage, black currant or a blend. Check all ingredients rather than treating GLA as the entire product. [1][3]

    Calculate GLA separately from capsule weight

    Imagine a label declares 1,000 mg oil standardized to 10% GLA. That corresponds to 100 mg GLA, assuming the percentage applies to the declared oil mass. It does not correspond to 1,000 mg GLA, and the calculation does not establish a treatment dose. [2]

    Hypothetical example — convert a hypothetical oil concentration
    Label itemAmount
    Total oil1,000 mg
    GLA fraction10%
    Calculated GLA100 mg
    GLA supplements: oil sources, evidence and label amounts — original article outline diagram
    Original editorial diagram of this article’s sections; no product photograph or clinical finding is depicted.

    Sources for this article

    1. Evening Primrose Oil: Usefulness and Safety | NCCIH
      Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.
    2. 6 Things To Know About Complementary Health Approaches for Rheumatoid Arthritis | NCCIH
      Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.
    3. Dietary Supplements: What You Need to Know
      Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.