At-home fatty-acid test: how it works, step by step

A fatty-acid test measures which fatty acids are in your blood, and in what proportions. That sounds technical, but the question it answers is simple: what does the fat balance of your diet look like, as your body has actually taken it up?

From fingertip to report

1. You order a test kit and it arrives by post.
2. You take the sample at home. A few drops of blood from your fingertip on a filter card, a so-called dried blood spot. The method has been validated against regular venous samples.[source pending] Follow the sampling guide to avoid the most common mistakes.
3. You post the card in the return envelope, ideally early in the week.
4. The laboratory analyses the fatty acids and builds a fatty-acid profile.
5. You get the report, usually after a few weeks.

The numbers in the report

The omega-6:3 ratio says how many parts omega-6 there are for each part omega-3. It gives a picture of overall fat balance.

The Omega-3 Index is EPA and DHA as a percentage of the fatty acids in red blood cells.[source pending]

The AA:EPA ratio compares arachidonic acid (omega-6) with EPA (omega-3), which partly compete for the same places in cell membranes.[source pending]

Many reports show other measures too, such as the split between saturated and unsaturated fatty acids. If a word is unfamiliar, look it up in the glossary.

Why the result reflects months, not days

Red blood cells live for about four months, and the fatty acids in their membranes are replaced gradually.[source pending] A fatty-acid test therefore gives a picture of your diet over the last season. That is useful: you don't need to change anything before the test, just eat as usual.

It also means changes take time to show. That is why a retest is usually planned around 120 days after the first.

What the test is not

• Not a diagnosis. It measures fatty acids. It says nothing about illness.
• Not an answer key for what to do. It shows where you are. What makes sense to do depends on the rest of your life.
• **Not an undisputed measure.

Read the full walk-through of what a test can and can't tell you.

What people do with the result

The most common step is adjusting the diet: more oily fish, a little less omega-6-heavy processed food, and an omega-3 plan that fits everyday life. Some do it on their own. Others want help reading the report and making a plan, then retesting to see whether it worked. That is what my coaching programs are about.

Is a fatty-acid test for you?

Take the free 2-minute check. It asks no health questions, and it tells you honestly whether a test makes sense for you right now.

Sources

1. [source pending] Source needed: validation of dried blood spot fatty-acid analysis against venous samples
2. [source pending] Source needed: original definition of the Omega-3 Index (EPA + DHA as % of red blood cell fatty acids)
3. [source pending] Source needed: review on arachidonic acid (AA) and EPA sharing the same enzymes and membrane positions
4. [source pending] Source needed: red blood cell lifespan (~120 days) and how fast membrane fatty acids change
5. [source pending] Source needed: review discussing the usefulness and limits of the omega-6:3 ratio as a marker