5 Mushroom Coffee Side Effects (What Can You Expect?)

Last updated on September 9th, 2025 at 10:23 am

Ever wondered if that trendy cup of mushroom coffee could do you more harm than good?

A few months ago, I shared my experience with mushroom coffee, how it gave me smoother energy without the usual crash. But here’s the thing: while I didn’t run into problems, not everyone has the same story.

Some people report bloating, jitters, or even medication interactions, which means the health perks come with fine print.

That’s where this guide comes in.

We’re going to break down the most common mushroom coffee side effects, why they happen, and what you can do to minimize them. By the end, you’ll know exactly what to watch for, and whether you should drink it or not.

5 Mushroom Coffee Side Effects

If you’re the type who likes to skim, here’s a quick table that breaks down the five most common side effects. For the full story, including tips and details, keep reading below.

1 – Digestive Discomfort (Bloating or Upset Stomach)

Usually, mushroom coffee digestive issues are about dose and timing. The fact is functional mushrooms (reishi, lion’s mane, cordyceps) are rich in beta-glucans, polysaccharides, and prebiotic fibers that can feed your gut bacteria.

That’s great long-term for microbiome balance. But on day one, it can feel like bloating, or even mild diarrhea.

My first go was a full scoop on an empty stomach (not a good idea!). Those fibers, combined with coffee acids (chlorogenic acids), hit fast, and the stomach upset felt like a mini-storm.

I learned to change one variable at a time:

Smaller serving, with food, and not stacking other gut-stimulating stuff (like magnesium citrate or MCT) in the same cup. Much calmer.

Different brands

Another thing people miss: blends aren’t standardized. One “teaspoon” from Brand A can pack more fruiting-body powder than Brand B.

If your cup suddenly feels harsher, it’s not in your head; concentration swings matter. Also, brewing style affects tolerance.

Brewing matters

A smoother traditionally brewed coffee base tends to sit better for me than ultra-concentrated espresso shots, which can be rough when your gut’s already learning new prebiotics.

Watch patterns

If bloating happens within 30–60 minutes, try moving your cup to mid-morning after breakfast. If it shows up hours later, it might be fermentation from the added fibers; spacing your intake or lowering the dose helps.

And don’t stack multiple adaptogens on day one. Instead, give your gut a clean A/B test so you know what’s doing what.

Tip: Start with ¼–½ serving mixed into food (oatmeal or a protein smoothie), sip slowly, and wait 48–72 hours before increasing. This lets your microbiome adapt and reduces bloating, gas, and stomach upset.

2 – Allergic Reactions or Sensitivities

If you’ve got a mushroom allergy or sensitivity, mushroom coffee is not your friend. Even though brands market reishi, lion’s mane, or cordyceps as “functional mushrooms,” your immune system doesn’t care.

These fungi contain unique compounds, such as polysaccharides, sterols, cordycepin, and erinacines. For sensitive people, those can trigger the same response you’d get from eating shiitake or button mushrooms.

Also, reactions range from mild to scary. Some people experience itchy skin or a rash. Meanwhile, others suffer from digestive upset, including bloating, nausea, or diarrhea.

In rare but serious cases, mushroom coffee could set off swelling, hives, or breathing difficulties. A

And because mushroom powders aren’t standardized. One cup might feel fine, and the next could have a higher dose of those compounds that push your body over the edge.

Interestingly, the 2024 research on mushroom coffee flagged allergies as one of the top contraindications. This alongside conditions like hypertension and histamine intolerance.

That makes sense, since certain mushroom bioactives can act as histamine triggers. That’s bad news if you already struggle with food sensitivities or intolerance.

Basically, what’s meant to help your body could accidentally send your immune system into overdrive.

Tip: If you’ve ever reacted to mushrooms, even a “mild” reaction, skip mushroom coffee altogether. It’s not worth gambling with your immune system.

Instead, stick to regular coffee or try caffeine-free alternatives like chicory or dandelion root coffee if you still want that earthy flavor without the allergy risk.

3 – Medication Interactions

It’s easy to assume that because it’s “just coffee with mushrooms,” there aren’t any risks. But functional mushrooms like reishi, cordyceps, and lion’s mane contain bioactive compounds.

For instance, polysaccharides, sterols, and even naturally occurring substances like lovastatin and ergosterol (the 2024 study found them in brewed mushroom coffee).

Anyway, these can interact with prescription meds in ways that aren’t always obvious.

• Blood thinners (e.g., warfarin): Some mushrooms, particularly reishi, have anticoagulant properties. Now, combine that with blood thinners, and you may end up with an increased risk of bleeding or bruising.
• Blood pressure drugs: Reishi has been linked to lowering blood pressure. On its own, that might sound like a perk. However, if you’re already on hypertension medication, mushroom coffee can push things too low. This may cause dizziness or lightheadedness.
• Diabetes medication: Mushrooms may influence blood sugar regulation. If you pair them with diabetes drugs, you could face episodes of hypoglycemia that are hard to predict.
• Immunosuppressants: Mushrooms like cordyceps stimulate immune function. If you’re taking medication designed to suppress your immune system, that benefit flips into a drawback. Plus, the mushrooms may counteract the drug’s effectiveness.

The frustrating part is that these interactions don’t always appear immediately. You might feel fine for weeks, then notice side effects creeping in.

Tip: If you take daily medication, always check with your doctor before trying mushroom coffee. A quick conversation can save you trouble later. As they say, “better safe than sorry.”

4 – Caffeine-Related Side Effects

One of the biggest reasons people switch to mushroom coffee is the promise of less caffeine. And that’s true; it commonly has about half the caffeine of a regular cup, depending on the brand and the amount of mushroom powder they blend in.

However, it’s not caffeine-free. If you’re someone who struggles with jitters, insomnia, anxiety, or heart palpitations, mushroom coffee can still stir up those same problems. In fact, the study (already mentioned) on mushroom coffee showed something interesting:

Adding mushrooms like Cordyceps militaris and Hericium erinaceus did reduce caffeine content compared to plain brewed coffee.

A traditional brew clocked in around 5.6 mg of caffeine per 200 mL, while mushroom blends dropped that number. That’s definitely a softer kick. However, it’s still enough to cause side effects if you’re caffeine-sensitive.

Another fact is that mushroom coffee doesn’t only deliver caffeine. It also brings in extra bioactive compounds like lovastatin (from lion’s mane) and ergosterol (from cordyceps).

Your body is juggling more than simply the caffeine hit. This can make reactions harder to predict. Some people find the mix smoother, while others feel the side effects more strongly than expected.

The tough part is that caffeine sensitivity is personal. For some, one cup in the morning feels amazing; for others, even a small dose leaves them wired at midnight.

Tip: If you know caffeine messes with your sleep or nerves, drink mushroom coffee earlier in the day and limit it to one cup. Or better yet, try mushroom-only blends (no coffee at all) from brands like Four Sigmatic or Ryze. You’ll still get the adaptogens and antioxidants without the caffeine crash.

5 – Uncertain Long-Term Effects

Here’s the thing: it’s still pretty new as a daily wellness drink. Sure, people have been drinking coffee for centuries, and medicinal mushrooms have a long history in traditional medicine.

But blending the two in concentrated powders and drinking them every morning? That’s a modern experiment, and the long-term effects aren’t fully understood yet.

The research mentioned comparing coffee with Cordyceps militaris and Hericium erinaceus fruiting bodies did show some exciting benefits.