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Supplements for ADHD: What the Trials Show for Omega-3, Iron, Zinc and L-Theanine

ADHD supplements don't replace medicine, behavioural therapy or parent training, so never stop, skip or trade your prescribed medicine for one. Omega-3 had little or no effect on parent-rated symptoms in children and teens (grade A). Iron helped a little in children with low iron stores, and zinc and vitamin D gave small drops in small trials (grade C). Skip St John's wort, and avoid stacking caffeine or energy products on stimulants.

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ADHD (attention deficit hyperactivity disorder) affects focus, impulse control and activity levels in children and adults. This guide covers what supplement trials show. It gives no amounts for children and no medicine doses.

Supplements don't replace ADHD treatment: medicine, behavioural therapy and parent training. Don't stop, skip or swap a prescribed medicine for a supplement; talk to the prescriber first. For a child, ask your child's doctor before giving any supplement.

The short version

  • Omega-3 (fish oil), children and teens, against placebo: no effect on parent-rated ADHD symptoms on high-certainty evidence. Grade A for little or no effect (Gillies 2023).
  • Iron, zinc, vitamin D: small trials, mostly in children; the iron benefit was in children with low iron stores, while the zinc and vitamin D trials did not select children who were low. Grade C (Konofal 2008; Talebi 2022; Gan 2019).
  • Saffron, pine bark extract, micronutrient formulas: one or a few small trials each. Grade C (Baziar 2019; Johnstone 2022).
  • St John's wort: no better than placebo in 54 young people, and it interacts with many medicines. Grade C (Weber 2008).
  • Caffeine and "energy" products on top of stimulant medicine: both raise heart rate and blood pressure; the only trials of caffeine with a stimulant were tiny 1980s studies of behaviour, not heart safety. The stimulant labels warn about heart effects (amphetamine label).
Supplement (who, compared with what)What trials foundSize of effectGrade
Omega-3 (children and teens, vs placebo)No change in parent-rated total symptoms16 trials, 1,166 peopleA
Zinc (children, vs placebo)Drop in total score (estimate from large to almost none), not in inattention or hyperactivity6 trials, 489 childrenC
Vitamin D (children on methylphenidate, vs placebo)Small drop in scores, low-quality evidence4 trials, 256 childrenC
Iron (children with low ferritin, vs placebo)Lower ADHD rating on iron23 childrenC
St John's wort (ages 6 to 17, vs placebo)No difference54 young peopleC

Does fish oil (omega-3) help ADHD?

Grade A for little or no effect in children and teens. A 2023 Cochrane review of 37 trials rated it high certainty that omega-3 and other polyunsaturated fats (PUFA) left parent-rated total ADHD symptoms (16 trials, 1,166 children and teens), inattention and hyperactivity no better than placebo. Low-certainty evidence from 3 trials (191 people) suggested more children may count as improved, and side effects probably did not differ (moderate certainty) (Gillies 2023). A separate pooling of 22 trials (1,789 people) found no clear overall effect, with a small benefit only in trials lasting at least 4 months (Liu 2023). The ADHD condition page shows B, "mixed", for fish oil; the high-certainty Cochrane result supports A for no meaningful effect. Trials in adults are few; for fish oil in general, see fish oil supplements.

Do iron, zinc, vitamin D or magnesium help ADHD?

Grade C, small effects. Only the iron trials tested people who were low, so ask for a ferritin test before iron; the zinc and vitamin D trials did not select children with low levels.

  • Iron: in 23 children aged 5 to 8 with ADHD and low ferritin (iron stores) but no anaemia, ADHD ratings fell on iron and not on placebo over 12 weeks; parent and teacher scales did not change significantly (Konofal 2008). In a 2025 pooling of trials in people without anaemia, iron did not improve attention; its other benefits held in people with iron deficiency and disappeared when they were left out (Fiani 2025). See iron supplements.
  • Zinc: across 6 trials (489 school-age children), total ADHD scores fell, though the estimate ranged from a large drop to almost none, and inattention and hyperactivity scores did not change, on moderate to very low certainty evidence (Talebi 2022). See zinc supplements.
  • Vitamin D: in 4 trials (256 children) where it was added to methylphenidate, scores improved slightly, on low to very low quality evidence (Gan 2019).
  • Magnesium: tested together with vitamin D in one 8-week children's trial, which found fewer emotional and conduct problems on a strengths-and-difficulties questionnaire than placebo (Hemamy 2021). No result separates magnesium's own effect.

Does L-theanine help ADHD?

Grade D: tiny, short studies in boys and teens, mostly with caffeine. In 5 boys aged 8 to 15, a single dose of L-theanine improved a cognition score, while caffeine alone worsened one measure of impulse control; the two together improved some attention measures (Kahathuduwa 2020). In a 2026 trial in 21 young people aged 10 to 19, a single high-dose L-theanine and caffeine mix and a single dose of methylphenidate each cut errors on one attention task against placebo; only the medicine sped reaction times (Nawarathna 2026). These trials were in young people, not adults. Can you take L-theanine with amphetamine or methylphenidate? No trial has looked at the pair as its question; in a 6-week trial in 98 boys aged 8 to 12 with ADHD, some on stimulant medicine, L-theanine was well tolerated and improved some sleep measures against placebo, though not the time taken to fall asleep (Lyon 2011). Ask your prescriber or pharmacist. See L-theanine.

Do saffron, pine bark extract or micronutrient formulas help?

  • Saffron: grade C. In 54 children, 6 weeks of saffron capsules or methylphenidate gave no significant difference in parent or teacher ratings; this was a small pilot, so it can't show the two are equal (Baziar 2019). In a 2026 trial in children aged 6 to 12 (43 finished), adding saffron to methylphenidate improved parent ratings but not attention or impulsivity scores on a computer test (reaction time improved); there was no placebo (Hosseinpourfardi 2026). See saffron.
  • French maritime pine bark extract: grade C. In one trial in 61 children, 4 weeks of the extract reduced hyperactivity and improved attention and concentration, while placebo did not; symptoms returned a month after stopping (Trebatická 2006). See pine bark extract.
  • Broad micronutrient formulas: grade C, mixed. In 126 children, 54% on a vitamin-mineral formula were rated improved by clinicians against 18% on placebo, but a parent-rated score combining ADHD, defiance, mood and peer problems improved by similar amounts in both groups, and the formula group grew 6 mm more (Johnstone 2022).

Does melatonin help sleep in ADHD?

Grade C for falling asleep sooner, not for ADHD symptoms. In 105 children aged 6 to 12 with ADHD and long-standing trouble falling asleep, 4 weeks of melatonin moved sleep onset about 27 minutes earlier and added about 20 minutes of sleep, with no change in behaviour or thinking against placebo (Van der Heijden 2007). For a child, ask your child's doctor. For adults, see sleep supplements compared.

Should you skip St John's wort and 5-HTP for ADHD?

St John's wort: grade C, no better than placebo. In 54 children and teens aged 6 to 17, 8 weeks of St John's wort improved inattention and hyperactivity no more than placebo (Weber 2008). It also speeds the breakdown of many medicines, including hormonal birth control, and can cause serotonin syndrome with antidepressants (can I take St John's wort with birth control?; with SSRIs?).

5-HTP: grade C, no benefit. In adults with high ADHD traits, a single dose did not reduce distractibility on any measure, and 19.6% of everyone given 5-HTP had fatigue, nausea or vomiting (Jackson 2026). See can I take 5-HTP with SSRIs?

Stimulants add to the risk. The amphetamine label warns that serotonin syndrome, which can be life-threatening, may occur when amphetamines are combined with serotonin-affecting products, and it names SSRIs, tryptophan and St John's wort among them. Signs include agitation, hallucinations, a fast heartbeat, sweating, flushing, high temperature, tremor, stiff or jerking muscles and poor coordination (amphetamine label).

Is it safe to stack caffeine with ADHD medicine?

Treat it as a harm risk. Stimulant medicines raise blood pressure (on average by about 2 to 4 mm Hg) and heart rate (about 3 to 6 beats a minute), some people more; the labels say to avoid them with serious heart disease and to monitor pulse and blood pressure (amphetamine label; methylphenidate label). Caffeine, pre-workouts and "energy" or "focus" blends add their own stimulant load; FDA cites 400 mg of caffeine a day as an amount not generally linked to negative effects for most adults, but says some medicines make people more sensitive to caffeine; it is not a safe allowance on top of a stimulant (FDA). The FDA also notes that medical experts advise against energy drinks for children and teens. Only tiny 1980s trials, such as one in 6 children, gave caffeine together with methylphenidate, and they measured behaviour, not heart safety (Garfinkel 1981). Watch for a racing heart, chest pain, anxiety and lost sleep, and see supplements for caffeine dependence.

The amphetamine label also says acidifying agents lower amphetamine blood levels and effect, while alkalinizing agents raise them, and it says to avoid taking amphetamine with stomach alkalinizers; ask your pharmacist which antacids count (amphetamine label).

What we'd skip

  • Omega-3 as an ADHD treatment in children and teens: no change in parent-rated symptoms on high-certainty evidence (Gillies 2023).
  • St John's wort and 5-HTP: no benefit in trials (Weber 2008; Jackson 2026), plus serotonin syndrome risk with amphetamine: the label names St John's wort and tryptophan, and 5-HTP acts the same way (amphetamine label).
  • L-tyrosine: in an old single-blind study, none of 7 children improved (Eisenberg 1988).
  • Lion's mane, ashwagandha and NAC "for focus": lion's mane has only lab work (Mohan 2025). Ashwagandha root extract lowered ADHD rating scores against placebo over 8 weeks in one 2026 trial in 58 children and teens with mild ADHD, a single small trial that has not been repeated (grade D) (Naik 2026). NAC has not been tested in ADHD itself: it lowered ADHD self-report scores in adults with lupus (Garcia 2013) and did not improve behaviour in youth with neurofibromatosis type 1, where two were withdrawn for worse behaviour (Gilbert 2026).
  • Iron without a blood test: the small benefits were in people who were low (Fiani 2025). The zinc and vitamin D trials did not test only low levels; ask whether a blood test makes sense first.

Safety and interactions

These limits are for adults; children's amounts are a decision for your child's doctor.

  • Iron: upper limit for adults, 45 mg of elemental iron a day, because more upsets the stomach and causes constipation; exceed it only if your clinician advises it after blood tests. Keep iron bottles away from children: an overdose can kill a young child (NIH ODS).
  • Zinc: the adult limit is 40 mg a day, since long-term excess can cause copper deficiency (NIH ODS).
  • Magnesium: adults should keep supplements at or under 350 mg a day, as more tends to cause diarrhoea (NIH ODS).
  • Vitamin D: adult upper limit 4,000 IU a day, because higher intakes can push blood calcium up; exceed it only with a clinician's advice and blood tests (NIH ODS; check your stack).
  • Serotonergic supplements with stimulants or antidepressants: St John's wort and tryptophan products carry the serotonin syndrome warning above.
  • Pregnancy and breastfeeding: ask your midwife or obstetric team before any of these.

When to see a doctor

  • Get emergency care for chest pain, fainting, or a racing or pounding heartbeat on stimulant medicine, or for signs of serotonin syndrome (agitation, high temperature, sweating, stiff or twitching muscles).
  • Get help now for thoughts of suicide or self-harm: in the US, call or text 988.
  • Tell the prescriber soon about new low mood, anxiety, tics or sleep problems, and, for children on medicine, poor appetite, weight loss or slowed growth.

Don't stop a prescribed medicine on your own; ask the prescriber or pharmacist. For anyone under 18, ask a clinician; if pregnant or breastfeeding, ask your midwife or obstetric team.

FAQ

What supplements help with ADHD? None replaces treatment. Small trials suggest iron may help a little in children with low iron stores, and zinc and vitamin D gave small drops in scores (grade C) (Konofal 2008; Talebi 2022), and omega-3 did not change parent-rated symptoms in children and teens (grade A) (Gillies 2023).

Does fish oil help kids with ADHD? A 2023 Cochrane review found high-certainty evidence that it did not change parent-rated ADHD symptoms in children and teens (grade A) (Gillies 2023). Ask your child's doctor before giving any supplement.

Can I take L-theanine with amphetamine (for example, mixed amphetamine salts)? No trial has looked at the pair as its question; in one 6-week trial of 98 boys with ADHD, some on stimulant medicine, L-theanine was well tolerated (Lyon 2011), and the theanine trials of ADHD symptoms were tiny and short (grade D) (Kahathuduwa 2020). Ask your prescriber or pharmacist first.

Does St John's wort help ADHD? No: it did no better than placebo in 54 children and teens (grade C) (Weber 2008), and the amphetamine label lists it among products that can cause serotonin syndrome when combined with amphetamine (amphetamine label).

Does melatonin help children with ADHD sleep? In 105 children with ADHD and trouble falling asleep, it moved sleep onset about 27 minutes earlier without changing behaviour (grade C) (Van der Heijden 2007). Ask your child's doctor about whether and how to use it.

Sources

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