Quick answer

Ask your pharmacist or doctor before combining. Official sources document 4 supplements for levodopa: iron, vitamin B6 and protein on the carbidopa and levodopa label, and BCAA products in studies. Levodopa and some amino acids share the same route across the gut wall, so protein products belong on the list as well as pills.^1,2,3,4

Key facts

The carbidopa and levodopa label says iron salts, including those in multivitamins, can bind levodopa and carbidopa and reduce how much is absorbed.¹
The label says levodopa competes with certain amino acids to cross the gut wall, so a high-protein diet may delay and reduce its absorption.³
In 7 volunteers, leucine placed in the small intestine cut levodopa absorption from about 40 percent to 21 percent.⁴
The label says carbidopa and levodopa can lower vitamin B6 levels and tells doctors to check them.²
MedlinePlus lists iron salts, and vitamins containing them, among the nonprescription products that may interact.⁵

What is levodopa for, and why would food or supplements matter?

MedlinePlus says levodopa is used for the symptoms of Parkinson's disease. The body turns it into dopamine in the brain, and carbidopa, usually prescribed with it, stops it from being broken down before it gets there. This page uses the combined medicine page because the two are normally taken together.⁵

Levodopa has to be absorbed from the gut, and the label says it shares a transport route with certain amino acids. That is why this page covers protein and amino acid products next to the vitamins and minerals you would expect.³

Does protein powder or a BCAA product change how levodopa is absorbed?

The label's wording is about diet. It tells people that a change to foods high in protein may delay absorption and lower the amount that reaches the blood.³

Ask your pharmacist or doctor first

Protein can lower how much levodopa is absorbed. The carbidopa and levodopa label says levodopa competes with certain amino acids to cross the gut wall, so a high-protein diet may delay its absorption and reduce the amount that reaches the blood.³

On the medicine's label

A protein powder or a BCAA product delivers amino acids in a concentrated form, which is why both are on this list, although the label itself speaks only of dietary protein. The BCAA entry is built from two studies. In 7 volunteers, leucine in the small intestine lowered levodopa absorption. In people whose response to levodopa fluctuated, high-protein meals or leucine, isoleucine or phenylalanine by mouth reversed the effect of levodopa given by drip, without lowering its level in the blood.^4,6

Ask your pharmacist or doctor first

Levodopa competes with certain amino acids for absorption from the gut, and its label says a high protein diet may reduce how much is absorbed. In studies, leucine cut levodopa absorption from the gut, and leucine or isoleucine taken by mouth reversed the effect of levodopa given by drip. The label does not name BCAA supplements, so ask your doctor or pharmacist before combining them.^4,6,7

Reported in studies

Can iron or a multivitamin with iron change levodopa?

NIH's iron sheet says some evidence in healthy people shows that iron supplements reduce levodopa absorption, possibly by binding it, and that US labels for levodopa warn about iron-containing dietary supplements. MedlinePlus lists the same group: iron salts and vitamins that contain them.^5,8

Ask your pharmacist or doctor first

Iron can bind levodopa and carbidopa in the gut and reduce how much the body absorbs, which can make the medicine less effective. The carbidopa and levodopa label says iron salts, including those in multivitamins, should be combined with it only with caution.^1,8,9

On the medicine's label

What does the label say about vitamin B6 and levodopa?

This entry has two parts that are easy to mix up. One is that vitamin B6 can undo the effect of levodopa taken alone, and that carbidopa blocks this. The other is that the pair can lower the body's own vitamin B6, so the label tells doctors to check levels. Which part applies depends on whether the medicine is levodopa alone or combined with carbidopa, so know exactly which one you have. MedlinePlus also asks people to tell their doctor about any past vitamin B6 deficiency.^2,5

Ask your pharmacist or doctor first

The carbidopa and levodopa label says pyridoxine at 10 to 25 mg can reverse the effects of levodopa taken on its own, and that carbidopa blocks this. The same label warns that carbidopa and levodopa can lower vitamin B6 levels, that seizures from low B6 have been reported, and that doctors should check B6 levels before and during treatment.²

On the medicine's label

Where does magnesium fit with carbidopa and levodopa?

Searches often ask about magnesium. None of the four entries is about magnesium, and the MedlinePlus page for the medicine does not mention it. The sources checked do not address it. That is not a finding either way, so ask your pharmacist. A multivitamin that also contains iron is a different case, because iron is covered above.⁵

How are the four levodopa entries tagged?

Three entries, iron, vitamin B6 and protein, are on the label. The BCAA entry rests on studies, because the label does not name amino acid supplements. All four are tagged ask first, and none is tagged avoid. Nothing in them is a reason to change a prescription on your own.

What should you ask your pharmacist about levodopa and supplements?

Is my medicine levodopa alone, or carbidopa and levodopa together?
Does my multivitamin contain iron or vitamin B6?
I use a protein powder or BCAA product. Does that change how I should take my doses?
Has anyone checked my vitamin B6 level since I started?
Which of my other products contain minerals I have not mentioned?

A written list of every supplement, with its Supplement Facts panel, makes this conversation faster.

Questions people ask

What vitamins interact with carbidopa levodopa?

Two vitamin products appear in the sources: vitamin B6 and multivitamins that contain iron. The label says carbidopa and levodopa can lower vitamin B6, and that iron salts, including those in multivitamins, can reduce absorption.^1,2

Does magnesium interfere with carbidopa levodopa?

The sources checked do not address it. That is not a finding either way, so ask your pharmacist.⁵

What are the levodopa nutrition interactions?

The label describes competition with amino acids, so a high-protein diet may delay and reduce absorption, and it warns about iron salts. Vitamin B6 is the third entry on the label.^1,2,3

Do protein shakes or BCAAs affect levodopa?

The label speaks of a high-protein diet, and studies found that leucine cut levodopa absorption. The label does not name BCAA supplements, so ask your doctor or pharmacist before combining them.^3,4

Which vitamins should not be taken with levodopa?

The sources document iron, including iron in multivitamins, and vitamin B6. Both are tagged ask first, which means checking with your pharmacist before you change anything.^1,2

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.