You may eat salmon every week, or you may not have touched oily fish in months. Either way, it is hard to know what that means inside the body. An omega-3 blood test turns those habits into numbers. The Omega 3/Omega 6 Profile in the BPR catalogue looks at the balance of these fatty acids in your blood, which can be a useful check if you are changing your diet or taking a fish oil supplement.
Omega-3 and omega-6 in a nutshell
Omega-3 and omega-6 are families of polyunsaturated fats. The body cannot make enough of some of them, so they need to come from food. The long-chain omega-3s, EPA and DHA, are found mainly in oily fish. The NHS recommends at least 2 portions of fish a week, including 1 of oily fish such as salmon, sardines, mackerel, herring, trout or pilchards, and notes that fresh and canned tuna do not count as oily fish. It also explains that long-chain omega-3 is important during pregnancy and breastfeeding, because it helps the baby's nervous system develop.
Omega-6 fats are also part of an ordinary diet. Neither family is "good" or "bad" on its own. The interest lies in the balance and in how much omega-3 actually reaches the body's cells.
What the profile measures
LML lists four markers in the Omega 3/Omega 6 Profile:
Omega-3 index
The omega-3 index is the proportion of EPA and DHA among all the fatty acids in red blood cell membranes. It was proposed as a marker linked to heart health and has been studied in many populations (von Schacky, 2014). Because red blood cells are replaced over a period of months, the index reflects longer-term intake rather than your last meal.
Omega-6 to omega-3 ratio
This ratio compares the two families. LML notes that a better balance, with relatively more omega-3, is generally considered favourable and has been linked with lower inflammation and heart and brain health. It is worth knowing that researchers debate how useful the ratio is on its own. One critical review argues that it says less than the omega-3 index, because very different diets can produce the same ratio (Harris, 2018). That is why the profile reports both.
AA:EPA ratio
This compares arachidonic acid (AA), an omega-6 fat, with EPA, an omega-3 fat. It is another way of looking at the balance between the two families.
Omega trans fat index
This reflects the share of trans fats in the blood.
How omega-3 levels vary
A 2024 update that mapped omega-3 levels in blood across many countries found large differences between populations (Schuchardt et al., 2024). Within any population, individual results also vary a lot. A test is the only way to see where you sit, instead of assuming.
When does the test tend to make sense?
People commonly look at their omega-3 status when they:
- eat little or no oily fish, for example on vegetarian or vegan diets;
- take a fish or algae oil supplement and want to see whether it is changing anything;
- are planning a pregnancy and want to review their diet with a professional;
- train regularly; interest in the omega-3 index as a marker in sport is growing (Medoro et al., 2024).
As a general guide, people who track their omega-3 index often retest every 6 to 12 months, which gives enough time for changes in diet or supplements to show. Talk to a professional about whether and how often the test is useful for you, especially if you take blood-thinning medicines or other supplements.
