FDA warns Parkinson’s patients and caregivers about vitamin B6 deficiency and seizure risk with carbidopa/levodopa

The FDA is requiring new warnings on drug products containing carbidopa and levodopa, a common treatment for Parkinson’s disease and some other forms of parkinsonism. The agency says these medicines can lead to vitamin B6 deficiency and, in some cases, vitamin B6 deficiency-associated seizures.

For patients and families, the practical message is not to panic and not to stop Parkinson’s medicine on your own. Instead, this is a reason to ask the prescribing clinician whether vitamin B6 testing and follow-up monitoring make sense, especially if there are new symptoms, nutrition problems, weight loss, or higher-dose or long-term treatment.

What changed

In its March 20, 2026 Drug Safety Communication, the FDA said it reviewed postmarketing cases and published medical literature and is now requiring labeling changes for carbidopa- or levodopa-containing products. The new warning is about vitamin B6 deficiency and related seizures.

The agency also advised clinicians to consider checking a baseline vitamin B6 level before starting treatment and to repeat testing from time to time during treatment, particularly in patients who may be more vulnerable to deficiency. If deficiency is found, supplementation may be needed under medical guidance.

What carbidopa/levodopa is used for

Carbidopa/levodopa is one of the most commonly prescribed medicines for Parkinson’s disease symptoms such as slowness, stiffness, and tremor. MedlinePlus notes that it is also used for certain types of parkinsonism, a group of conditions that can cause movement problems similar to Parkinson’s disease.

Levodopa helps replace dopamine in the brain. Carbidopa is added to help more levodopa reach the brain and to reduce some side effects such as nausea. Because this combination is widely used, even an uncommon safety issue matters for patients, caregivers, and clinicians.

What the FDA found

The FDA did not say that most people taking carbidopa/levodopa will develop vitamin B6 deficiency or seizures. Instead, the warning reflects a safety signal serious enough to require updated labels and closer monitoring.

Published reports in the medical literature help explain why the agency acted. Recent case reports in Neurology and other journals describe patients with Parkinson’s disease who developed severe vitamin B6 deficiency and seizures while taking carbidopa/levodopa. In some of those reports, seizures did not improve as expected until vitamin B6, also called pyridoxine, was given.

That is clinically important because it suggests the deficiency itself may be part of the problem in some patients, not just the seizure alone.

Symptoms patients and caregivers should watch for

Vitamin B6 deficiency can be easy to miss at first because symptoms may be vague. The FDA and case reports point to the need to watch for signs such as:

Numbness or tingling
Weakness
Irritability or unusual mood changes
Mouth soreness or cracks at the corners of the mouth
A sore or swollen tongue
Symptoms of anemia, such as unusual fatigue, paleness, shortness of breath, or feeling lightheaded
Unexplained worsening that does not fit a person’s usual Parkinson’s pattern

Seizure symptoms can include shaking, staring spells, loss of consciousness, sudden confusion, or not responding normally. Seek urgent medical help right away for a seizure, loss of consciousness, or sudden severe confusion.

In older adults, seizure symptoms may not always look dramatic. Caregivers may notice a sudden change in awareness, repeated blank staring, unusual jerking, or a person seeming suddenly much more confused than usual.

Who may be at higher risk

Based on the FDA communication and the published case reports, the risk may be higher in people with other reasons for low vitamin B6. These can include poor nutrition, unintentional weight loss, malabsorption problems, alcohol use disorder, dialysis, pregnancy, and other conditions or situations that can lower vitamin levels.

The reports also suggest that longer use or higher doses may matter in some cases, although the available evidence does not yet show exactly how often this happens or predict who will be affected.

That uncertainty is important. Most of the published evidence behind the seizure concern comes from case reports. Case reports are useful for spotting rare or serious problems, but they cannot prove how common a problem is or establish cause and effect with the same confidence as large controlled studies.

Why patients should not stop treatment on their own

Carbidopa/levodopa is often essential for daily function. Stopping it suddenly can worsen Parkinson’s symptoms and can sometimes cause serious complications. If you take this medicine and are worried about the new warning, the safest next step is to contact the clinician who prescribes it.

That conversation may include whether to order vitamin B6 testing now, whether repeat monitoring is needed later, whether diet could be contributing, and whether supplementation is appropriate. Patients should not start vitamin B6 supplements on their own without asking first, because the right dose and follow-up plan depend on the person’s overall health, medicines, nutrition, and lab results.

What remains uncertain

Several questions are still unanswered. The FDA communication does not establish a precise incidence rate for vitamin B6 deficiency or seizures in people taking carbidopa/levodopa. The published literature includes small numbers of patients, and many had additional risk factors that may have contributed.

So this is best understood as an important warning and a monitoring issue, not evidence that the medicine is unsafe for most patients or that everyone taking it will develop a deficiency.

What this means for readers

If you or a family member takes carbidopa/levodopa, it is reasonable to ask at the next visit whether vitamin B6 testing should be done now or added to future monitoring. Bring up symptoms such as tingling, weakness, mouth soreness, fatigue, mood changes, weight loss, or other unexplained changes.

Most important, do not stop Parkinson’s medicine on your own. Talk with the prescribing clinician about your personal risk, nutrition, testing, and whether supplementation is needed. And if a seizure, fainting, or sudden severe confusion happens, seek urgent medical care.

Sources

This article is for general informational purposes only and is not medical advice. Research findings can be early, limited, or subject to change as new evidence emerges. For personal guidance, diagnosis, or treatment, consult a licensed clinician. For current outbreak or public health guidance, follow your local health department, the CDC, or another relevant public health authority.