3 Supplements to Avoid Mixing With Vitamin C

Vitamin C tends to be popular during the winter when people reach for it to help support their immune system. If you take vitamin C, it’s worth knowing that some supplements can interfere with how well it works.

1. Vitamin B12

Some research suggests that high doses of vitamin C might degrade or reduce B12 levels. But more recent studies have found that it doesn’t make a huge difference if you take them together.

Healthcare providers and supplement makers may still recommend spacing out vitamin C and B12 supplements by a few hours instead of taking them at the same time.

2. Copper Supplements

Copper is an essential mineral your body needs to make red blood cells, support connective tissue, and convert sugar into energy.

If you’re taking a copper supplement to support your immune or nervous system—or to help with iron levels, which copper is sometimes used for—you may want to avoid taking it at the same time as vitamin C.

Some animal studies suggest that vitamin C can interact with copper ions, potentially increasing oxidative stress. At high doses, it could cause damage in major organs, such as the kidneys.

Some supplement manufacturers also caution that vitamin C may chelate copper, meaning it could reduce how well the mineral is absorbed. If you take both supplements, it may help to avoid large doses (unless prescribed by your doctor) and space them a few hours apart.

3. Aluminum (Ingredient)

Aluminum isn’t a dietary supplement, but it’s commonly found in over-the-counter medications used to relieve indigestion or acid reflux.

Vitamin C can increase how much aluminum your body absorbs from these products, which may raise the risk of excess aluminum exposure. High levels aren’t ideal for kidney health and have been linked to other potential health concerns. If you take vitamin C and use an aluminum-containing antacid, it’s a good idea to space them out.

Does Dairy Intefere With Vitamin C?

Dairy is only a concern if you’re taking vitamin C specifically to improve iron absorption, since calcium can interfere with how well iron is absorbed. If you’re taking vitamin C for its own health benefits, you generally don’t need to worry about taking it with dairy or other calcium-containing foods.