Strattera Dosage: Weight-Based Dosing and the 6-Week Window

If you’re starting Strattera (atomoxetine), you probably want to know within a week whether it works. The dosing schedule runs on a slower clock, and the dose you land on depends on your weight, your genes, and how carefully the first weeks are read.

Atomoxetine is thought to work by blocking the norepinephrine transporter, the pump that recycles a chemical messenger involved in attention and alertness, according to the Strattera prescribing information. Your liver clears it mainly through an enzyme called CYP2D6. People born without working copies of that enzyme clear it far more slowly: their half-life is about 21.6 hours instead of 5.2, and their total exposure to the drug is about 10 times higher.

The standard schedule rests on solid evidence. In two randomized adult trials with 280 and 256 participants, atomoxetine improved both inattentive and hyperactive-impulsive symptoms more than placebo over 10 weeks. The results are real, and the dosing chart built from trials like these is well tested.

But a dosing chart can’t tell you how to read the weeks between steps, and at Siggy we believe a medication that builds slowly deserves steady follow-up rather than a single verdict at the first check-in. This guide covers how the dose is calculated, why it climbs slowly, what the 2026 label changed for poor metabolizers, and why week 6 works best as a checkpoint. The right Strattera dose comes from reading the first few months carefully, not from the number on the first prescription.

What This Page Covers

• The Standard Strattera Dosing Chart
• How Weight-Based Dosing Works for Kids and Teens
• Why the Dose Climbs Slowly
• The 6-Week Assessment Window
• Poor Metabolizers and the 2026 Label Change
• Missed Doses, Stopping, and Safety Checks

The Standard Strattera Dosing Chart

The label’s dosing table splits people by body weight, with one schedule for children and teens under 70 kg (about 154 pounds) and another for heavier teens and all adults.

Group	Starting Dose	Target Dose	Maximum Dose
Ages 6 and up, under 70 kg	0.5 mg/kg a day	1.2 mg/kg a day	1.4 mg/kg or 100 mg, whichever is less
70 kg or more, and all adults	40 mg a day	80 mg a day	100 mg a day
CYP2D6 poor metabolizer or strong inhibitor	Same as weight group	Same as weight group	Same, reached in 4-week steps

For most people, each increase comes after at least 3 days at the previous dose. For CYP2D6 poor metabolizers and people taking a strong CYP2D6 inhibitor, the label recommends 4 weeks between increases instead. For adults, the label allows a move from 80 mg to 100 mg only if the response still isn’t optimal after 2 to 4 more weeks, and it notes no data showing better results above 100 mg.

You can take the daily total as one morning dose or split it evenly between morning and late afternoon or early evening, with or without food. Swallow the capsules whole, because the powder inside irritates the eyes. Brand-name Strattera has been discontinued, and an FDA Federal Register notice confirmed that wasn’t for safety or effectiveness reasons, so generic atomoxetine follows this same label dosing.

Liver function changes the math too. Moderate liver impairment (Child-Pugh B) doubles atomoxetine exposure, so the starting and target doses drop to half. Severe impairment (Child-Pugh C) quadruples exposure, so they drop to a quarter.

How Weight-Based Dosing Works for Kids and Teens

For children 6 and older who weigh less than 70 kg, the dose comes straight from body weight. A child who weighs 30 kg (about 66 pounds) would start around 15 mg a day, aim for about 36 mg, and stay under about 42 mg. Capsules come in 10, 18, 25, 40, 60, 80, and 100 mg strengths and aren’t meant to be opened, so the actual dose is the closest practical match to that math.

Going past the target rarely helps. The label reports no added benefit above 1.2 mg/kg a day, and a fixed-dose trial showed the tradeoff: 19.3% of children on 1.2 mg/kg and 29.1% on 1.8 mg/kg lost at least 3.5% of their body weight, compared with 1.3% on placebo. That’s why height and weight get tracked throughout treatment.

The label also carries a boxed warning for children and teens. In short-term pediatric studies, suicidal thoughts occurred in 0.4% of those taking atomoxetine versus 0% on placebo, all in children 6 to 12 and all within the first month. A similar analysis in adults didn’t show increased risk. Families should watch closely for mood or behavior changes, especially early and after dose changes. In a crisis, call 911 or call or text 988.

Why the Dose Climbs Slowly

Stomach side effects are the most common early complaint. In the label’s pooled adult trials, nausea affected 26% of people on atomoxetine versus 6% on placebo, and decreased appetite affected 16% versus 3%. Every schedule starts low and holds for at least 3 days before the target dose.

Splitting the dose may help too. In pediatric studies, nausea affected 13% of children on once-daily atomoxetine versus 4% on placebo, compared with 7% versus 6% in studies that used twice-daily dosing. Those numbers came from separate studies rather than a head-to-head test, but splitting the dose is worth asking about if nausea lingers. Adults in the pivotal trials took atomoxetine twice a day, and their average final dose was about 48 mg twice daily.

Each increase is also a checkpoint for your heart. The label calls for heart rate and blood pressure checks before starting, after each dose increase, and periodically during treatment. For a closer look at the early weeks, see our guide to Strattera side effects in the first month.

The 6-Week Assessment Window

The label’s own timeline explains why a week or two is too early to judge. On the standard schedule, at least 3 days at the starting dose, then 2 to 4 weeks at the target before considering the maximum, puts the first dose decision around weeks 3 to 5. Allow a week or two after that step, and week 6 is the first point where you and your prescriber can fairly judge the dose.

Week 6 is a checkpoint, though, because the effect keeps growing. A pooled adult trial analysis of two studies found atomoxetine separated from placebo at week 1, but the effect was still small at week 4 and reached a moderate size by week 26, with response rates climbing the whole time. A clinical review of atomoxetine’s response pattern describes the same arc: onset within 1 to 2 weeks for some people, then gradual gains for up to 24 weeks or longer.

Early numbers can’t predict your outcome, either. A 2016 predictor analysis of pooled adult trials found that improvement at weeks 4 and 10 predicted later response statistically, but not reliably enough for clinical decisions, and that response sometimes has to be judged over more than 10 weeks.

A useful week 6 check covers a few things:

• Symptom change, including what a partner, parent, teacher, or coworker has noticed
• Whether you’ve reached the target dose and taken it consistently
• Side effects such as nausea, appetite loss, sleep changes, sexual side effects, or trouble urinating
• Heart rate and blood pressure readings
• Any new medication that could change how atomoxetine is cleared

Poor Metabolizers and the 2026 Label Change

About 7% of White people and about 2% of Asian and Black people are CYP2D6 poor metabolizers, according to the label. A standard dose produces much higher drug levels in their bodies, and in adult trials their heart rate rose more, by 11 beats per minute on average versus 7.5 in other metabolizer types. Taking a strong CYP2D6 inhibitor creates a similar situation: paroxetine raised atomoxetine exposure 6.5-fold, and fluoxetine raised it 6- to 8-fold. Bupropion is also a strong inhibitor, which our Strattera vs Wellbutrin comparison covers.

For years, the label told prescribers to start these patients at the usual dose and raise it to the target only if symptoms failed to improve after 4 weeks. Some dosing guides still repeat that rule, which comes from older versions such as the 2022 Strattera prescribing information. The June 2026 label keeps the same starting, target, and maximum doses for poor metabolizers and people on strong CYP2D6 inhibitors. It recommends a 4-week interval between increases if symptoms haven’t improved and the dose is well tolerated, and it now explicitly suggests considering genetic testing to determine CYP2D6 status.

Pharmacogenetics experts take a complementary view. The Clinical Pharmacogenetics Implementation Consortium guideline notes that poor metabolizers may respond more strongly to a given dose because of their higher drug levels. When symptoms haven’t improved after about 2 weeks and side effects are absent, it suggests clinicians consider a blood level check to guide dose changes, though these checks aren’t routine. Our guide to genetic testing for psychiatric medications explains how these tests work.

Missed Doses, Stopping, and Safety Checks

If you miss a dose, take it as soon as you remember, but don’t take more than your prescribed daily total in any 24-hour period. When it’s time to stop, the label says no taper is needed, and studies found no withdrawal syndrome. ADHD symptoms can return, so stopping is still a conversation with your prescriber.

Call your prescriber promptly for any of these:

• Itching, dark urine, yellowing skin or eyes, right upper belly pain, or unexplained flu-like symptoms, which can signal rare liver injury
• Chest pain with exertion, fainting, or a racing heartbeat
• Trouble urinating, or an erection lasting more than 4 hours
• New aggression, agitation, or signs of mania

For chest pain, fainting, or an erection lasting more than 4 hours, get emergency care right away.

With a medication judged over months, the pattern of small changes is the evidence.

A weekly note on focus, sleep, appetite, and side effects turns week 6 into a look at the trend instead of an effort to piece it together from memory.

Atomoxetine’s dosing rewards careful math, steady follow-up, and patience through the first few months. For another non-stimulant with a different timeline, see our guide to guanfacine for ADHD, sleep, and focus.

Ready to take control of your mental health? Start your anonymous intake with Siggy and get your plan reviewed by a licensed prescriber.

This article is for education only and isn’t a substitute for personal medical advice. Talk with your own clinician before starting, changing, or stopping any medication.