Most people who start drinking olive oil experience zero side effects. The ones who do experience them almost always see them resolve within a few days as their body adjusts. But knowing what to expect, and why it happens, helps you avoid the discomfort entirely or manage it quickly if it shows up.
This guide covers every documented side effect of drinking olive oil, why each one occurs, who's most likely to experience it, and the specific steps to minimize or prevent each one. If you're already taking daily olive oil shots or considering starting, this is the reference you'll want to have.
For the broader benefits and risks overview, see Drinking Olive Oil: Benefits, Risks & How Much Is Safe. For getting started, see How to Drink Olive Oil: A Beginner's Guide. This article focuses specifically on the potential side effects.
The Most Common Side Effect: Digestive Adjustment
The single most reported side effect is temporary digestive discomfort in the first few days. This can include mild nausea, loose stools, stomach cramping, or an urgent need to use the bathroom. However, it's not a sign that something is wrong. It's just your digestive system responding to a concentrated dose of fat it isn't used to receiving all at once.
Why It Happens
Olive oil stimulates bile release from your gallbladder. Bile is what your body uses to digest and absorb fat. When you drink a tablespoon of oil on an empty stomach, your gallbladder contracts to release bile rapidly, and if your body isn't accustomed to that stimulus, the sudden bile release can accelerate intestinal motility. That's the mechanism behind the loose stools and urgency some people report.
This is actually the same mechanism that makes olive oil effective for constipation relief. A 2014 Journal of Renal Nutrition study found that just one teaspoon daily softened stools significantly. The "side effect" and the "benefit" are the same biological process, just experienced differently depending on your starting point.
How to Minimize It
Start small. Begin with one teaspoon (5mL) rather than a full tablespoon (15mL). Give your body 3–5 days to adjust, then increase to two teaspoons, then to a full tablespoon. Most digestive discomfort comes from starting at too high a dose.
Take it with food. Drinking olive oil alongside a meal, or immediately before eating, buffers the bile response. The oil mixes with other food in your stomach rather than hitting your small intestine as a concentrated fat bolus. If you're taking it in the morning, have it right before breakfast rather than 30 minutes before.
Try it at night instead. Some people find taking olive oil before bed produces fewer digestive symptoms because the body processes it slowly during sleep. Intestinal motility naturally slows at night, which counteracts the bile-stimulation effect. See Taking Olive Oil at Night.
Add lemon juice. The olive oil and lemon juice shot isn't just for taste. Lemon juice stimulates digestive enzymes independently of bile, which can help your body process the oil more efficiently. The vitamin C also enhances polyphenol absorption, so you're not trading health value for comfort.
Timeline: For most people, digestive adjustment takes 3–7 days. If symptoms persist beyond two weeks, reduce the dose and consult your doctor.
Nausea
Some people experience mild nausea after drinking olive oil, particularly on an empty stomach. This is separate from the digestive motility issue. It's a stomach sensation, not an intestinal one.
Why It Happens
Concentrated fat triggers cholecystokinin (CCK) release, a hormone that signals fullness but can also trigger nausea in sensitive individuals, especially when the stomach is otherwise empty. High-polyphenol EVOO also has a strong peppery flavor from oleocanthal which is the same compound that has been show to provide anti-inflammatory benefits, and can irritate the throat and trigger a mild gag reflex in some people.
How to Minimize It
Never take it on a completely empty stomach if you're prone to nausea. A few crackers, a piece of bread, or even a few sips of water beforehand can make a significant difference.
Chill the oil. Cold olive oil is less pungent and the oleocanthal burn is reduced at lower temperatures. Keep your Hoji packets in the refrigerator.
Chase it. Follow the shot immediately with lemon water, a bite of bread, or a piece of fruit. The lemon shot method works well here since the citrus flavor masks the oil and gives your mouth something else to focus on.
Switch to nighttime. Nausea from olive oil is almost exclusively a morning/empty-stomach phenomenon. Nighttime consumption after dinner rarely produces nausea because there's already food in your stomach.
Caloric Impact
This isn't a "side effect" in the medical sense, but it's the concern people raise most often: olive oil is 120 calories per tablespoon. Will drinking it daily cause weight gain?
The Evidence
The PREDIMED trial participants consumed 4+ tablespoons of olive oil daily, significantly more calories from fat than the control group, and lost more weight. The weight loss research consistently shows that olive oil's oleic acid triggers OEA, a natural satiety signal that reduces overall calorie intake by making you feel fuller. The calories from the oil are offset by reduced consumption elsewhere.
That said, this works when olive oil replaces other fats (butter, seed oils, dressings), not when it's added on top of an already high-calorie diet. One to two tablespoons daily as a replacement for less healthy fats is the evidence-backed approach. See How Much Olive Oil Should You Drink a Day for the dosage guide.
Gallbladder Sensitivity
People with gallbladder issues, gallstones, previous gallbladder removal, or biliary disease, may experience more pronounced side effects from drinking olive oil. The bile-stimulation mechanism described above is more intense when the gallbladder is compromised.
With gallstones: The rapid bile contraction triggered by a concentrated fat dose could potentially cause a gallstone attack in people with existing stones. If you have diagnosed gallstones, consult your doctor before drinking olive oil in concentrated doses.
After gallbladder removal: Without a gallbladder, bile drips continuously into the small intestine rather than being released in controlled bursts.
Allergic Reactions (Rare)
True olive oil allergy is extremely rare but does exist. Symptoms would include hives, swelling, difficulty breathing, or anaphylaxis - the same symptoms as any food allergy. If you've never consumed olive oil before and experience any allergic symptoms, stop immediately and seek medical attention.
More common than true allergy is sensitivity to the oleocanthal burn. The peppery throat sensation from high-quality EVOO is not an allergic reaction, it's mainly oleocanthal activating TRPA1 receptors in your throat (the same compound that provides ibuprofen-like anti-inflammatory benefits). The stronger the burn, the higher the oleocanthal content, and the greater the health benefit. It feels alarming the first time but is completely harmless.
Can You Drink Too Much Olive Oil?
Technically yes, but you'd have to try hard. There is no established "toxic dose" of olive oil. The practical upper limit is set by caloric density and digestive tolerance, not by toxicity.
The PREDIMED trial used 4+ tablespoons daily (approximately 480 calories from olive oil alone) with positive health outcomes. The FDA health claim is based on 1.5 tablespoons daily. For most people, 1–2 tablespoons as a shot plus olive oil in cooking is the evidence-backed sweet spot which is enough to get the documented health benefits without excessive caloric intake.
Signs you're overdoing it: persistent loose stools (not just the first week), unintended weight gain, or feeling uncomfortably full. The solution is simple -> reduce the dose. See How Much Olive Oil Should You Drink a Day.
Who Should NOT Drink Olive Oil
For the vast majority of healthy adults, drinking olive oil is safe. But certain groups should avoid it or consult their doctor first:
People with active gallstone attacks or acute biliary disease. The bile-stimulation effect could worsen symptoms.
People with fat malabsorption disorders. Conditions like chronic pancreatitis, celiac disease (unmanaged), or short bowel syndrome may impair fat digestion to the point where concentrated oil causes significant discomfort.
Children under 12. There's limited research on concentrated olive oil doses in young children. Using olive oil in cooking is fine, but the concentrated shot format is untested in pediatric populations.
Anyone about to undergo surgery. Olive oil's mild blood-thinning and blood-pressure-lowering effects mean most surgeons recommend stopping olive oil intake (beyond normal cooking use) 1–2 weeks before planned surgery.
For safety during specific life stages, see Olive Oil During Pregnancy. For pet safety: Dogs and Cats.
The Side Effects You WANT
Worth noting: most of olive oil's "side effects" are actually benefits in disguise. The bile stimulation that causes initial digestive adjustment is the same mechanism that improves long-term gut health. The oleocanthal throat burn that seems alarming is the anti-inflammatory compound working. The fullness that feels excessive at first is the OEA satiety signal that supports weight management. The mild blood pressure reduction is cardiovascular protection.
The adjustment period is real but temporary. The benefits are real and compound over time. Harvard tracked people for 28 years. The PREDIMED trial ran for 5 years. The people in those studies didn't stop after a week of digestive adjustment. See What Happens If You Drink Olive Oil Every Day for the day-by-day timeline of what to expect.
The Quick-Start Protocol to Minimize All Side Effects
Days 1–3: One teaspoon (5mL) with food. This dose rarely produces any side effects in anyone.
Days 4–7: Two teaspoons (10mL) with food. Most people tolerate this without issues.
Week 2: One tablespoon (15mL) which is the full dose. With or without food, depending on your tolerance.
Week 3+: Experiment with timing. Try morning on an empty stomach, before bed, or find your best time. By now your body has adjusted and you can optimize for preference rather than tolerance.
If you experience discomfort at any stage, drop back to the previous dose for another 3–5 days. There's no rush. The benefits come from consistency over months and years, not from hitting a high dose in week one.
FAQ
Does drinking olive oil cause diarrhea?
It can cause loose stools in the first few days, especially if you start with a large dose on an empty stomach. This is bile stimulation, not a sign of illness. Start with one teaspoon with food and increase gradually. Most people adjust within a week. If you already struggle with diarrhea, start at a smaller dose or take it with meals.
Is it safe to drink olive oil every day?
Yes, for most healthy adults. The PREDIMED trial participants consumed 4+ tablespoons daily for 5 years with improved health outcomes. The FDA health claim is based on 1.5 tablespoons daily. See Can You Drink Olive Oil? Safety Guide and Is Drinking Olive Oil Good for You?
Can olive oil cause stomach pain?
Mild cramping is possible during the adjustment period, especially on an empty stomach. It's caused by bile contraction and usually resolves within a few days. Taking olive oil with food eliminates stomach discomfort for most people.
What happens if you drink too much olive oil at once?
Nausea, digestive urgency, and loose stools. Not dangerous, just uncomfortable. If this happens, reduce your dose and increase gradually. There's no toxicity risk from olive oil at any realistic dose.
The Bottom Line
Olive oil's side effects are primarily mild, temporary, and almost entirely preventable with the right approach: start small, take it with food, increase gradually. The adjustment period is measured in days, but the studied benefits are measured in years.
Hoji makes the daily habit simple: lab-tested, polyphenol-verified, single-origin EVOO in sealed single-serve 10 mL packets.
Related Guides
Getting started: How to Drink Olive Oil: A Beginner's Guide
The complete reference: Drinking Olive Oil: Benefits, Risks & How Much Is Safe
Safety guide: Can You Drink Olive Oil? Everything About Safety
Dosage: How Much Olive Oil Should You Drink a Day?
Best time: Best Time to Take Olive Oil
Daily timeline: What Happens If You Drink Olive Oil Every Day
The science: Olive Oil Shot Benefits: What Science Says
Shot of olive oil a day: Benefits, Dosage & Best Practices
Is it good for you? Is Drinking Olive Oil Good for You?
What does it do? What Does Drinking Olive Oil Do?
The lemon combination: Olive Oil and Lemon Juice Shot
Cholesterol: Drinking Olive Oil for Cholesterol
Health benefits: Olive Oil Health Benefits: What Science Actually Proves
