Chemotherapy and Supplements: What You Need to Know Before Mixing Them

When you're undergoing chemotherapy, a powerful medical treatment used to kill cancer cells, often with serious side effects. Also known as cancer treatment, it works by targeting fast-growing cells—but it doesn’t always distinguish between cancerous and healthy ones. Many people turn to supplements, products like vitamins, herbs, or minerals taken to support health. Also known as herbal remedies, they’re often seen as harmless or even protective. But here’s the truth: supplements aren’t regulated like drugs. What’s on the label isn’t always what’s inside, and many can interfere with how chemotherapy works—sometimes making it less effective, sometimes making side effects worse.

Take vitamin C, for example. Some people take high doses hoping to boost immunity during chemo. But studies show it can protect cancer cells from oxidative damage, which is exactly how some chemo drugs kill tumors. Then there’s St. John’s wort, a common herb for mood support. It speeds up how your liver breaks down drugs, which can drop chemo levels in your blood to ineffective amounts. Even something as simple as green tea extract or garlic pills can thin your blood and increase bleeding risk during treatment. And don’t assume natural means safe—many supplements are made in unregulated factories with inconsistent dosing, contaminants, or undisclosed ingredients.

Doctors don’t always ask about supplements because they assume patients won’t mention them. But if you’re taking anything—whether it’s melatonin for sleep, turmeric for inflammation, or a multivitamin from the grocery store—you need to tell your oncology team. They can check for known interactions with your specific chemo drugs. For instance, if you’re on taxanes like paclitaxel, certain antioxidants might reduce their effectiveness. If you’re on platinum-based drugs like cisplatin, magnesium supplements could affect kidney function. It’s not about avoiding all supplements—it’s about knowing which ones are safe, which ones to pause, and when to restart after treatment.

The posts below cover real cases and science-backed advice on how supplements interact with medications, including chemo. You’ll find details on what to avoid, what might help without risking your treatment, and how to talk to your doctor without sounding like you’re pushing alternative medicine. There’s also advice on reading labels, spotting hidden ingredients, and understanding why some "natural" products are riskier than prescription pills. This isn’t about fear—it’s about control. You’re already fighting cancer. Don’t let a supplement unknowingly fight against you.