Mushroom Coffee Side Effects: Is It the Coffee or the Mushroom?

The most common mushroom coffee side effects are mild bloating and caffeine jitters. Both usually fade within 1 to 2 weeks. Rarer risks include allergic reactions, kidney stones linked to chaga and a handful of reported liver injury cases.

A few people should hold off: anyone pregnant or breastfeeding, anyone with a kidney stone history, anyone with liver problems and anyone on blood thinners or diabetes drugs.

Is it the coffee or the mushroom? Find your culprit

Mushroom coffee side effects always have 2 suspects. This table tells you which one to check first:

A swap test settles it. Drink regular coffee for 3 days instead. If the mushroom coffee side effects vanish, the mushrooms are the cause. If they stay, it's the caffeine.

Coffee side effects: caffeine, jitters and sleep

Caffeine causes most mushroom coffee side effects. Mushroom coffee still has caffeine. Most blends land around 40 to 60 mg per cup. Some go up to 100 mg. Here's how that compares:

Jitters and a racing heart are the classic caffeine-driven mushroom coffee side effects. They follow when your daily total runs high. Headaches show up when you drink too much, or when you skip your usual cup.

Caffeine also lingers. Half of it can still be in your system 5 hours later, so a 3 pm cup can wreck your night. Our guide to mushroom coffee caffeine has the full numbers by brand.

Mushroom side effects: ingredient by ingredient

Each mushroom brings its own possible mushroom coffee side effects. Here's what to know about the 4 most common ones.

Lion's mane

Lion's mane causes few mushroom coffee side effects. Stomach upset and headaches are the main reports. Allergic reactions are rare.

Chaga

Chaga is behind the most talked-about mushroom coffee side effects. It's very high in oxalates. Oxalates can raise the risk of calcium oxalate kidney stones, the most common type.

Most people never notice. But a 2020 case report described end-stage kidney disease in a person after long-term chaga use. So with a stone history, check with your doctor before any chaga product (that includes our chaga range).

Reishi

Reishi adds its own mushroom coffee side effects. It's linked to calm and sleep. It may thin the blood a little, so it can stack with blood thinners. Reishi has also appeared in liver injury case reports.

Cordyceps

Cordyceps is the energy mushroom. It may lower blood sugar and slow clotting. 

Can mushroom coffee damage your liver?

Only rarely. Liver injury is the rarest of the reported mushroom coffee side effects. The evidence is case reports. In 2024 and 2025, doctors presented several cases of liver injury in people drinking mushroom coffee at American College of Gastroenterology meetings, including this 2025 abstract.

Case reports show something happened to a few individuals. They can't show how often it happens or prove the coffee caused it. The risk looks low for healthy adults.

Stop and see a doctor if you notice yellow skin or eyes, dark urine or pain under your right ribs. Anyone with liver disease should ask a doctor before trying mushroom coffee.

How strong is the evidence on mushroom coffee side effects?

Research on mushroom coffee side effects is thin. Most claims borrow from studies on mushroom extracts or on coffee alone.

Mushroom coffee side effects by health condition

Is mushroom coffee safe with high blood pressure?

Ask your doctor first. Raised blood pressure is one of the caffeine-related mushroom coffee side effects. Caffeine can push readings up for a few hours. Track your home readings after a small cup to see how you respond.

Is mushroom coffee OK with anxiety or palpitations?

A 40 mg blend is gentler than a 95 mg brewed cup. Decaf blends go lower still. Start there.

Is mushroom coffee OK with IBS or a sensitive stomach?

Start with a quarter serving. Pick fruiting body extract with no grain fillers, since grain is a common bloating trigger.

Is mushroom coffee safe in pregnancy?

Data on concentrated mushroom extracts in pregnancy is limited. Ask your doctor. Keep total caffeine under about 200 mg a day.

Does mushroom coffee help with weight loss?

Research doesn't show that mushroom coffee burns belly fat. Weight changes come from food and movement.

Can people with celiac disease drink it?

Check the label. Some powders are grown on grain. Leftovers end up in the jar.

Who should avoid mushroom coffee?

These groups face the highest risk of mushroom coffee side effects:

• Pregnant or breastfeeding: data on concentrated extracts is limited
• Kidney stone history: chaga's oxalates are the concern
• Liver conditions: see the case reports above
• Blood thinners or diabetes drugs: possible interactions
• Mushroom or mold allergy: higher risk of a reaction

At the pharmacy counter, try this: "I'm thinking of drinking a coffee with lion's mane and chaga daily. Does that clash with anything I take?"

The 60-second mushroom coffee risk check

This check screens your risk of mushroom coffee side effects. Answer yes or no to each:

1. Are you pregnant or breastfeeding?
2. Have you ever had kidney stones?
3. Do you have liver disease?
4. Do you take blood thinners or diabetes medication?
5. Do you have a known mushroom or mold allergy?
6. Does 1 regular coffee already make you jittery?

Any yes on questions 1 to 5 means talk to a doctor or pharmacist first. A yes on question 6 means start with a quarter serving or a decaf blend. All no? Move on to the plan below.

Do mushroom coffee side effects differ by brand?

Yes. 2 jars can look identical and behave nothing alike. Grain fillers, untested batches and hidden doses all raise the odds of mushroom coffee side effects.

Our Lion's Mane and Chaga espresso blend lists 100% Arabica with 2 fruiting body extracts and no fillers or binders. You can compare it with the rest of our mushroom coffee range.

The 14-day plan to avoid mushroom coffee side effects

A slow start is the easiest way to head off mushroom coffee side effects.

Track your mushroom coffee side effects as you go. Each night, write down 4 things: serving size, sleep quality, stomach comfort and mood. Mild symptoms that fade mean you keep going. Symptoms that build mean you drop back a step for 3 days.

When to stop and see a doctor

Stop drinking it and call a doctor for any of these:

• Yellow skin or eyes with dark urine
• Severe stomach pain
• Swelling of the face or lips
• Symptoms that last past 2 weeks

Trouble breathing needs emergency care right away.

FAQs about mushroom coffee side effects

Is mushroom coffee safe to drink every day?

For most healthy adults, 1 cup a day is fine. Watch your total caffeine and take a break if stomach or sleep symptoms build.

Can mushroom coffee cause bloating?

Yes. Bloating is one of the most common mushroom coffee side effects. Extract fibres and coffee acid cause gas in the first week, so start with a quarter serving.

Can mushroom coffee cause kidney stones?

Chaga contains oxalates, which can raise the risk of one type of kidney stone. Most people are fine. Anyone with a stone history should ask a doctor first.

Can mushroom coffee cause an allergic reaction?

Yes, though it's uncommon. Itching or rash can appear in people allergic to fungi. Get medical help if swelling or breathing trouble shows up.

Why do I feel sick after mushroom coffee?

Nausea is one of the early mushroom coffee side effects. Usually it's a full serving on an empty stomach. Drop to a quarter serving and drink it with food.

Mushroom coffee side effects: the bottom line

Mushroom coffee side effects are mostly mild and fade once your gut and caffeine intake settle. Take the risk check, follow the 14-day plan and talk to a doctor about anything that worries you.

Disclaimer: This article is for general information and isn't medical advice.