Leqembi (lecanemab) is given as an intravenous infusion once every two weeks, with each session lasting about one hour. The dose is 10 mg/kg, meaning it’s calculated based on your body weight. A newer option, a weekly self-administered injection, is also now available for maintenance treatment.
The IV Infusion Process
For the standard route, a healthcare provider places an IV line in your arm and delivers the medication over approximately one hour. The solution is weight-based, so the clinic calculates your specific dose beforehand and mixes it into a saline bag. You’ll sit or recline during the infusion while staff monitor you for any reactions.
This happens every two weeks on an ongoing basis. Most infusion visits, including check-in and a brief observation period afterward, take roughly 90 minutes to two hours total. You’ll need someone to be aware of your schedule since this is a long-term commitment, not a short course of treatment.
The Subcutaneous Autoinjector Option
Leqembi is also approved as a once-weekly subcutaneous injection using a prefilled autoinjector called IQLIK. This version delivers a fixed 360 mg dose into the skin of the abdomen, upper thigh, or back of the upper arm. It’s designed for maintenance treatment, meaning you’d typically start with IV infusions first, then transition to the weekly self-injection.
The safety profile in clinical trials was similar between the IV and subcutaneous routes. The autoinjector absorbs about 53% of the drug compared to the IV route, which is why it’s given more frequently (weekly instead of every two weeks) at a different dose. For many patients, the convenience of a home injection versus biweekly clinic visits is a significant practical advantage.
MRI Monitoring Schedule
Before starting Leqembi, you’ll need a baseline brain MRI taken within the past year. This scan gives your care team a reference point for detecting a side effect called ARIA, which involves temporary brain swelling or tiny bleeds that can occur with this class of drug.
The FDA recommends MRI scans before your 3rd, 5th, 7th, and 14th infusions. That means frequent imaging in the early months of treatment, when ARIA is most likely to develop. These scans often detect changes before you’d notice any symptoms, which is why the monitoring schedule is front-loaded. If swelling or bleeding does appear on a scan, your doctor may pause or adjust treatment.
Infusion Reactions and What They Feel Like
About 1 in 4 patients (24.5%) experience an infusion-related reaction at some point during treatment. That sounds high, but most people who react only have it happen once. The typical symptoms resemble a mild flu: fever, chills, body aches, feeling shaky, and joint pain. Some people experience nausea, vomiting, or temporary blood pressure changes.
If a reaction happens during your infusion, the care team can slow the drip rate or stop it entirely and treat symptoms on the spot. For future sessions, you may be given antihistamines, acetaminophen, or anti-inflammatory medications beforehand to prevent a repeat reaction. These pre-medications are not routine for everyone but are added if you’ve had a previous reaction.
ARIA Symptoms to Watch For
ARIA (amyloid-related imaging abnormalities) is the most closely watched risk with Leqembi. It comes in two forms: brain swelling and small brain bleeds. Many cases show up only on MRI with no noticeable symptoms. When symptoms do occur, they can include headache, confusion, dizziness, vision changes, nausea, weakness, or in rare cases, seizure.
Your genetic profile affects your risk. Patients who carry certain forms of the APOE gene, particularly those with two copies of the ε4 variant, face a higher chance of developing ARIA. Genetic testing before starting treatment helps your care team weigh the risks and plan monitoring accordingly.
What to Expect Before Your First Infusion
The process begins well before your first IV bag is hung. You’ll need a confirmed diagnosis of early Alzheimer’s disease with evidence of amyloid plaques in the brain, typically confirmed through a PET scan or spinal fluid test. A baseline MRI is required to check for any pre-existing brain bleeds or swelling. Genetic testing for APOE status is also part of the workup.
Once cleared, your clinic will schedule your biweekly infusions. Each dose is prepared fresh from refrigerated vials, diluted in saline, and given through a filtered IV line. The medication cannot be frozen or shaken during preparation, as that can damage the protein structure of the drug. From a practical standpoint, plan for a recurring half-day commitment every two weeks during the IV phase, factoring in travel, infusion time, and the MRI appointments that are woven into the early months of treatment.