There is no single “right age” to start taking fish oil. Omega-3 fatty acids are essential at every stage of life, but whether you need a supplement depends more on your diet, health status, and life stage than on hitting a specific birthday. Infants can begin getting omega-3s through breast milk or formula from birth, children can start supplements as early as 6 months when they begin solid foods, and healthy adults who eat fish regularly may not need a supplement at all.
Infants and Toddlers: Starting at 6 Months
Babies need omega-3s from the very beginning for brain and eye development. In the first six months, breast milk or formula supplies those fats. Once an infant starts eating solid foods, typically around 6 months, parents can introduce omega-3 oil by mixing half a teaspoon to one teaspoon (about 2.5 to 5 ml) into cereal, soup, or porridge.
The NIH sets adequate intake for total omega-3s at 0.5 grams per day for babies up to 12 months. From ages 1 to 3, the recommendation shifts to 0.7 grams per day of ALA, the plant-based omega-3 found in foods like flaxseed and walnuts. At this age, the body converts small amounts of ALA into the longer-chain omega-3s (EPA and DHA) found in fish oil, though the conversion rate is low. That’s why many pediatricians suggest a DHA-containing supplement or DHA-fortified foods for toddlers who don’t eat fish.
Children and Teenagers: 4 to 18 Years
Omega-3 needs climb as kids grow. The adequate intake for ALA rises from 0.9 grams per day for children ages 4 to 8, to 1.0 to 1.2 grams per day for those 9 to 13 (slightly higher for boys), and 1.1 to 1.6 grams per day for teenagers 14 to 18. These numbers cover ALA from food, not EPA and DHA specifically, because no official upper or lower target has been set for those longer-chain fats in children.
That said, research on teenagers and mood is worth noting. Multiple trials have tested fish oil in young people with depression. In one 12-week trial involving adolescents aged 13 to 24, those who received omega-3 supplements alongside standard treatment showed significantly greater improvement in depressive symptoms compared to those on standard treatment alone. Separate trials in children as young as 6 have found similar reductions in depression scores after 12 to 16 weeks of supplementation. The International Society for Nutritional Psychiatry Research considers 1 to 2 grams per day of EPA (one of the two main fats in fish oil) an effective dose for depression, though these guidelines were written for adults and the pediatric evidence is still limited in scale.
For a generally healthy child or teen who eats fish once or twice a week, a supplement isn’t necessarily needed. For picky eaters or kids who avoid seafood entirely, a children’s fish oil or algae-based omega-3 supplement can help fill the gap.
Adults: Diet Matters More Than Age
For adults 19 and older, the adequate intake for ALA is 1.6 grams per day for men and 1.1 grams per day for women. During pregnancy, that rises to 1.4 grams, and during breastfeeding, 1.3 grams. Again, no official daily target exists for EPA and DHA specifically. Most expert groups recommend eating fatty fish (salmon, mackerel, sardines, herring) at least twice a week as the preferred way to get those fats.
If you’re a healthy adult wondering whether to take a fish oil capsule for heart protection, the evidence is surprisingly thin. The American Heart Association’s 2026 dietary guidance states plainly that fish oil supplementation alone has not been demonstrated to lower cardiovascular disease risk in otherwise healthy adults, and in some people it may even be associated with an increased risk of a type of irregular heartbeat called atrial fibrillation. The AHA has never recommended fish oil pills for primary prevention in the general population, meaning people who don’t already have heart disease.
Where fish oil does carry a reasonable recommendation is for people who already have heart disease. The AHA considers omega-3 supplements reasonable for secondary prevention, specifically reducing the risk of death from coronary heart disease in people with an existing diagnosis. The same applies to patients with heart failure with reduced pumping function.
Pregnancy and Breastfeeding
DHA is critical for fetal brain development, particularly during the third trimester when the baby’s brain grows rapidly. Many prenatal vitamins include 200 to 300 mg of DHA for this reason. Women who are pregnant or breastfeeding and don’t eat fish regularly benefit the most from supplementation. The omega-3s you consume pass directly to your baby through the placenta and later through breast milk.
Older Adults and Brain Health
Many people in their 50s and 60s start fish oil hoping to prevent dementia. The reality is more nuanced. No clinical trial has been large and long enough to prove that DHA or fish oil supplements reduce the risk of developing dementia outright. Studies lasting up to five years have found no protection against cognitive decline in healthy older adults.
There is a potential window, though. People who already have mild cognitive impairment, the stage between normal aging and dementia, may see modest cognitive benefits from omega-3 supplementation. Some researchers interpret this as evidence that intervention needs to start early, before significant brain changes take hold. Genetics also play a role: people who carry a specific gene variant linked to higher Alzheimer’s risk (APOE4) appear to respond differently to omega-3s than non-carriers, though the optimal approach for each group remains unclear.
The dose of DHA that might benefit the brain has not been established. Published studies have used anywhere from 180 mg to 2,000 mg per day, and the best dose likely varies from person to person.
How Much Is Too Much
The NIH has not set a formal upper limit for omega-3 intake from supplements. However, most regulatory bodies consider up to 3 grams per day of combined EPA and DHA from supplements to be safe for adults. Higher doses, sometimes prescribed for very high triglyceride levels, should be taken under medical supervision because they can increase bleeding risk and, as noted, may raise the chance of atrial fibrillation.
Common side effects at moderate doses are mild: fishy aftertaste, digestive discomfort, or loose stools. Taking capsules with meals and storing them in the freezer can reduce the fishy burps that make many people abandon the supplement.
Deciding Whether You Actually Need a Supplement
The question isn’t really “what age” but “what situation.” A 25-year-old who never eats seafood may benefit more from a fish oil supplement than a 60-year-old who eats salmon twice a week. Here’s a practical way to think about it:
- Infants starting solids (6+ months): A small amount of omega-3 oil mixed into food supports brain development, especially if breastfeeding has stopped.
- Children and teens who avoid fish: A children’s omega-3 supplement can help cover DHA needs during years of rapid brain growth.
- Pregnant or breastfeeding women: A prenatal DHA supplement is widely recommended regardless of diet.
- Healthy adults who eat fish regularly: A supplement is unlikely to add measurable benefit for heart health.
- Adults with existing heart disease: Fish oil supplements carry a reasonable evidence base for reducing cardiac death risk.
- Older adults worried about memory: The evidence for prevention in healthy people is weak, but those already noticing mild cognitive changes may see modest benefit.