On a good ashwagandha label you will see a phrase like "standardised to 5% withanolides." It is one of the most useful pieces of information on the pack, yet rarely explained. This guide breaks down exactly what it means, as a matter of composition and quality.
For transparency: ashwagandha (Withania somnifera) is a botanical with no authorised health claims in the UK. This article explains what standardisation means, not what the herb does for health.
What withanolides are
Withanolides are the characteristic compounds of ashwagandha, the marker compounds the plant is measured by. According to a review retrieved from PubMed, withanolides are the principal metabolites of Withania somnifera, and importantly their availability and amount differ with tissue type and chemotype (the genetic variety of the plant) (Pandey et al., 2017, DOI). That natural variability is the whole reason standardisation exists.
What "standardised to 5%" actually means
Standardisation means the extract has been processed and measured so that a defined percentage of it is made up of the marker compounds, in this case withanolides. "Standardised to 5% withanolides" means that, by weight, 5 percent of the extract is withanolides, verified by testing. So if you take 600 mg of a 5% extract, roughly 30 mg of that is withanolides.
The key benefit is consistency. Because the raw plant varies so much by variety and growing conditions, standardisation ensures each batch and each capsule delivers a known, repeatable amount of the marker compounds rather than unpredictable raw powder.
Higher percentage is not automatically better
It is tempting to assume a higher withanolide percentage is always superior, but it is more nuanced. A very high percentage can indicate heavy concentration or, in some cases, different starting material or methods. What matters is that the figure is stated, verified, and that you know what part of the plant it came from. Root-only extracts, for example, are described differently from those using leaf, which we cover in what is KSM-66 ashwagandha.
How to read the figure sensibly
Treat the standardisation percentage as a transparency and consistency signal. A product that states its withanolide percentage and the plant part used is giving you the information to compare like with like. A product that says only "ashwagandha powder" with no figure leaves you guessing about how much of the marker compounds you are actually getting. We also discuss timing in when to take ashwagandha and cautions in ashwagandha safety and considerations.
How our ashwagandha is formulated
Our Ashwagandha uses KSM-66, a standardised root extract, described transparently by its withanolide standardisation, alongside L-theanine and vitamin B6. It is the consistent, composition-based way to present an ashwagandha supplement.
The takeaway
"Standardised to 5% withanolides" means the extract has been measured so that 5 percent of it, by weight, is the marker withanolide compounds, giving a consistent, known amount in every dose. Because the raw plant varies so much by variety and tissue, standardisation is what turns variable raw material into a reliable, comparable product.
Sources retrieved from PubMed; see linked DOI above. This article is for general information and composition education, not medical advice. Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. If you are pregnant, breastfeeding, taking medication or managing a medical condition, speak to your GP or pharmacist before starting a new supplement. Signed, Dr. Miron, Founder of Pure Vitamins UK.
