Vyvanse (lisdexamfetamine) causes side effects in most people who take it, with decreased appetite, insomnia, dry mouth, and irritability being the most frequently reported. The severity and type of side effects depend on your dose, your age, and how long you’ve been taking the medication. Most common side effects are manageable, but some, particularly cardiovascular and psychiatric effects, require closer attention.
Vyvanse is a prodrug, meaning it doesn’t become active until your body converts it. After you swallow it, red blood cells break it down into its active form (d-amphetamine) through a gradual, rate-limited process. This produces a slower rise in brain stimulation compared to immediate-release stimulants, with a peak drug level about 50% lower than an equivalent dose of standard amphetamine. That smoother curve is why Vyvanse generally causes fewer spikes in side effects, but it doesn’t eliminate them.
The Most Common Side Effects
In clinical trials, the side effects reported at rates of 5% or higher (and at least twice the rate of placebo) were:
- Decreased appetite and weight loss
- Insomnia
- Dry mouth
- Irritability
- Nausea and vomiting
- Diarrhea
- Upper abdominal pain
- Dizziness
- Anxiety
Appetite suppression is the hallmark side effect. Vyvanse increases the same brain chemicals responsible for its therapeutic effect, and those same chemicals directly dampen hunger signals. Many people find that eating a substantial breakfast before the medication kicks in and shifting their largest meal to the evening (after it wears off) makes this more tolerable. For children especially, tracking weight over time matters because sustained appetite loss can affect growth.
Insomnia is the second most disruptive effect for many users. Because Vyvanse is designed to last 10 to 14 hours, taking it too late in the morning can push its activity window into bedtime. Most people find that taking it first thing in the morning, ideally before 8 or 9 a.m., keeps sleep disruption to a minimum.
Effects on Heart Rate and Blood Pressure
Stimulants raise both heart rate and blood pressure. For most people on Vyvanse, this increase is modest, but the effect is consistent and dose-dependent. Long-term studies in children found no clinically meaningful changes in blood pressure or heart rhythm over time at standard doses. Still, people with pre-existing heart conditions, structural heart defects, or uncontrolled high blood pressure face a different risk profile. Irregular heartbeat (arrhythmia) is a less common but recognized cardiovascular side effect.
Psychiatric Side Effects
Vyvanse can cause mood and behavioral changes that range from mild to serious. The less common side effects listed in prescribing data include rapidly changing moods, euphoria, dysphoria (a persistent sense of unease or dissatisfaction), paranoia, depersonalization, and being quick to overreact emotionally. These tend to be dose-related and often improve with an adjustment.
The more serious psychiatric concern is psychosis or mania. The FDA added warnings to stimulant labels after reviewing reports of hallucinations and psychotic symptoms in children. A large study published in the American Journal of Psychiatry found that people using prescription amphetamines had roughly 2.7 times the odds of experiencing psychosis or mania compared to non-users. A clear dose-response pattern emerged: higher doses carried substantially greater risk. At doses above 30 mg of dextroamphetamine equivalents (which corresponds to about 100 mg of Vyvanse, well above the typical dose range), the odds of psychosis or mania increased more than fivefold.
For context, the standard dose range for most adults is 30 to 70 mg. Notably, the same study found that methylphenidate (Ritalin, Concerta) was not associated with increased psychosis risk, suggesting this is specific to the amphetamine class rather than stimulants in general. If you experience any hallucinations, paranoid thinking, or manic episodes while taking Vyvanse, that warrants immediate medical attention.
Growth Suppression in Children
Decreased weight is one of the most frequently reported side effects in pediatric patients, and the FDA’s prescribing information includes a specific warning about growth suppression. This means Vyvanse can slow both weight gain and height gain in children who take it continuously over months or years. The mechanism is straightforward: chronic appetite suppression leads to reduced caloric intake during critical growth periods. Pediatricians typically monitor height and weight at regular intervals, and some families use “drug holidays” during school breaks to allow catch-up growth, though the evidence on that strategy is mixed.
The Crash as It Wears Off
Many people experience a rebound period as Vyvanse leaves their system. This “crash” typically hits about 30 to 60 minutes before the medication fully wears off and lasts roughly an hour. During this window, you might feel a sudden drop in energy, heightened irritability, emotional sensitivity, or a surge of hyperactivity. Children in particular may have outbursts, crying spells, or anger that seems out of proportion to the situation. This isn’t a sign that the medication isn’t working; it’s the brain readjusting as stimulation drops.
Vyvanse’s gradual conversion process makes its crash milder than what people typically experience with immediate-release stimulants, but it doesn’t prevent it entirely. Some people find that eating a protein-rich snack as the medication winds down softens the transition.
Sexual Side Effects
Changes in libido and sexual function are recognized side effects of Vyvanse, though they’re less commonly discussed. The effects vary widely between individuals. Some people report increased sexual desire, while others experience the opposite. Reduced sexual satisfaction and changes in orgasm intensity have also been reported. These effects are common across amphetamine-class medications and tend to be dose-dependent.
Abuse Potential and Dependence
Vyvanse carries an FDA boxed warning, the most serious category of safety alert, for abuse, misuse, and addiction. As an amphetamine-based medication, it can produce euphoria (especially at higher doses) and carries a real risk of psychological and physical dependence with prolonged use. The prodrug design reduces this risk compared to immediate-release amphetamines because snorting or injecting the pill doesn’t speed up the conversion process, making it harder to get a rapid high. But the risk isn’t zero. Stopping Vyvanse abruptly after regular use can produce withdrawal symptoms including fatigue, depression, and sleep disturbances.
Less Common but Notable Effects
A handful of side effects show up less frequently but are worth knowing about. Constipation affects some users, likely due to the medication’s effect on gut motility. Headaches are common, particularly in the first weeks. Some people experience unusual drowsiness, which seems counterintuitive for a stimulant but can happen as the medication’s effects fluctuate throughout the day. Depersonalization, a feeling of being detached from yourself or your surroundings, is rare but reported in prescribing data.
Many side effects are most pronounced during the first few weeks and gradually improve as your body adjusts. Dry mouth, nausea, and dizziness in particular tend to fade with time. Appetite suppression and insomnia, on the other hand, often persist for as long as you take the medication, though most people develop partial tolerance.