14 Side Effects of Amoxicillin

Medically reviewed by Alan Carter, PharmD on May 19, 2016Written by Healthline Editorial Team and Ana Gotter

Amoxicillin side effects


There are 14 known side effects for amoxicillin (Amoxil, Trimox). These are:

  • breathing problems
  • dark urine
  • diarrhea
  • stomach upset
  • headache
  • dizziness
  • trouble sleeping
  • seizures
  • unusually weak or tired
  • unusual bleeding or bruising
  • yellowing of the eyes or skin
  • trouble passing urine, or a decrease in the quantity of urine

Allergic reactions like skin rash, itching, hives, or swelling of the face, lips, or tongue

allergic reaction

Allergies aren’t always the reason for a negative reaction to a drug. In fact, allergic reactions are a rare occurrence. Though it may seem like an allergic reaction, it is really a nonallergic adverse reaction. The most common causes of nonallergic adverse reactions are anticonvulsants, aspirin and NSAIDS, vaccines, diabetes meds, and chemotherapeutic agents.

Mild allergic reactions include skin rash, itching, and hives. Mild allergic reactions aren’t too worrisome on their own but should be observed in case symptoms worsen. Mild symptoms can be treated with antihistamines and hydrocortisone.

Swelling of the face, lips, tongue, and shortness of breath are signs of a severe allergic reaction. If you experience a severe allergic reaction, seek medical attention immediately.

If an allergic reaction occurs, monitor the spreading of the rash or redness. Amoxicillin can cause delayed allergic reactions even after you’ve stopped taking them.

Breathing problems



If you have difficulty breathing, you could be experiencing an allergic reaction to amoxicillin.

If you’re experiencing mild breathing problems, you can try to ease breathing by doing the following:

  • Breathe through pursed lips, which slows down breathing and allows for deeper breaths.
  • Perform activities at a comfortable pace; avoid rushing.
  • Try not to hold your breath.
  • Sit in front of a fan.

If you are allergic to amoxicillin or penicillin, inform your doctor so you can be prescribed another medication to prevent this reaction. If breathing becomes increasingly difficult, contact your doctor right away.


Diarrhea is loose, watery, and frequent stool. Diarrhea is considered chronic when you have had loose or frequent stools for more than four weeks.

Drink plenty of fluids to avoid becoming dehydrated. Drinking milk may be fine for mild diarrhea. For moderate and severe diarrhea, electrolyte solutions available in drugstores are usually best.

Diarrhea is a common side effect of amoxicillin. To help prevent it, take your doses with a meal. Avoid foods that could upset your stomach, like dairy or high-fiber foods.

To treat diarrhea caused by amoxicillin, supplement with probiotics and stay hydrated.

Diarrhea is typically considered a common side effect, but if you’re becoming dehydrated or noticing streaks of blood in the diarrhea, get professional medical attention immediately.

Stomach upset


Almost everyone experiences pain in the abdomen at one time or another. Most of the time, it is not caused by a serious medical problem. Stomach discomfort is a common side effect of amoxicillin. Symptoms include abdominal pain, nausea, and vomiting.


To cope with an upset stomach, eat bland, easy to digest foods like soups, crackers, and toast. Peppermint is thought to help upset stomach symptoms. You can take antinausea medication if necessary.

If you experience severe, prolonged abdominal pain or see blood in your vomit or stool, seek medication attention immediately.


A headache is pain or discomfort in the head, scalp, or neck. The most common headaches are most likely caused by tight, contracted muscles in your shoulders, neck, scalp, and jaw.

Headaches are a common side effect of taking amoxicillin, and while less serious, are a frequent occurrence.

Taking your dosages with food and drinking lots of water can help prevent headaches caused by amoxicillin. Regular exercise, getting enough sleep, and managing stress may also help.

Headache and migraine medications, including Tylenol and Aleve, can help to relieve headaches caused by amoxicillin.


Dizziness occurs when you feel lightheaded, like you might faint, being unsteady, or experiencing a loss of balance or vertigo (a feeling that you or the room is spinning or moving).


Tell your doctor all medications you are currently taking before they prescribe you amoxicillin. To prevent dizziness, avoid drinking alcohol when on amoxicillin.

Avoiding driving until you know how amoxicillin will affect you. If you get dizzy, sit down for a moment and see if it passes. Keep your head elevated with a pillow if you lie down.

Dizziness may be a symptom of anemia, or an allergic reaction.

If dizziness is severe, or combined with symptoms like shortness of breath or swelling of the lips, face, or tongue, a severe allergic reaction could be present. Seek immediate medical attention.

Redness, blistering, peeling, or loosening of the skin, including inside the mouth


Blisters are small, raised lesions where fluid has collected under the skin. They may be caused by an allergic reaction, burns, frostbite, or by excessive friction or trauma to the skin. Blisters may also be a symptom of a systemic illness, or of a specific skin disorder.

This side effect is somewhat rare, but serious when it does occur. If you experience redness, blistering, or peeling or loosening of the skin after taking amoxicillin, contact your doctor right away.

Mild, nonitching rashes may be managed by home treatment when not severe. Treatment includes antihistamines or hydrocortisone, oatmeal baths, and drinking lots of water. If skin starts blistering, peeling, or loosening, however, seek medical attention immediately.

To prevent severe irritations of the skin, do not take amoxicillin if you’re allergic to penicillin.

Yellowing of the eyes or skin

yellowing of skin

Jaundice is a yellow color in the skin, the mucous membranes, or the eyes. The yellow pigment is from bilirubin, a byproduct of old red blood cells. If you’ve ever had a bruise, you may have noticed that the skin went through a series of color changes as it healed. When you saw yellow in the bruise, you were seeing bilirubin.

This effect, and liver damage or injury, can also be caused by amoxicillin. The liver injury can even occur after amoxicillin doses have stopped. This is more likely to happen when taking amoxicillin with clavulanate.

Corticosteroids can be used to treat this side effect. Recognizing early symptoms such as fatigue, poor appetite, and vomiting can help prevent jaundice from worsening, Talk to your doctor if you experience any of these symptoms.

Do not take amoxicillin if you have or have ever had liver damage.

Trouble sleeping

Sleeping difficulty, called insomnia, can involve difficulty falling asleep when you first go to bed at night, waking up too early in the morning, and waking up often during the night.

Everyone has an occasional sleepless night, and this is not a problem for most people. However, as many as 25 percent of Americans report occasional sleeping problems, and insomnia is a chronic problem for about 10 percent of people.

Dark urine

Normal urine is often a pale or straw yellow color. When urine color strays from this color, it is considered abnormal. Abnormally colored urine may be cloudy, dark, or blood-tinged.

Any changes in urine color, or the presence of an abnormal urine color that cannot be linked to the consumption of a food or drug, should be reported to your doctor. This is particularly important if it happens for longer than a day or two, or you have repeated episodes.

Dark urine can be caused by amoxicillin due to changes in blood, liver, and/or kidney function. Renal toxicity is rare (occurring in approximately .03 percent of patients), but when it does occur, it can be serious.

Those at risk for kidney complications in particular should not use amoxicillin to prevent this side effect and potential kidney damage. Your doctor can prescribe another type of antibiotic.

If you are prescribed amoxicillin, make sure to only take the prescribed dose within the amount of time that is suggested by your doctor. It’s also important to drink the recommended requirement of water.

Dark urine is a severe side effect of amoxicillin. Talk to your doctor if you experience changes in your urine.


A seizure is a sudden change in behavior characterized by changes in sensory perception (sense of feeling) or motor activity (movement) due to an abnormal firing of nerve cells in the brain. Epilepsy is a condition characterized by recurrent seizures that may include repetitive muscle jerking called convulsions.

If you are experiencing this side effect, contact your doctor as soon as possible.

Trouble passing urine or change in the amount of urine


Pain on urination is a fairly common problem. It is most often caused by an infection in the urinary tract.

Amoxicillin may cause crystals to form in the urine. These crystals are directly tied to the amoxicillin, and look very different than crystals otherwise commonly found in urine. It can also happen in rare cases where the kidney is negatively impacted.

To prevent this, never take more than your prescribed dose and drink plenty of water. If you’re experiencing slight discomfort when you urinate, drink water and reduce the amount of protein in your diet.

Painful urination can also indicate renal failure or damage. Contact your doctor right away if you are experiencing this.

Unusual bleeding or bruising

redness and blistering


Amoxicillin can increase the risk of bleeding. If you’re experiencing either unusual bleeding or bruising, see a doctor immediately. Internal bleeding may be occurring, which could lead to bleeding in the digestive system, or, in rare cases, the brain.

To prevent this, make sure your doctor knows if you’re on anticoagulants or blood thinners before you start taking amoxicillin.

If you experience this as a side effect of amoxicillin, it’s considered to be a rare but serious side effect. Seek medical attention as soon as possible.

Unusually weak or tired



If your fatigue falls under the category of “excessive tiredness,” this is a serious side effect. It’s uncommon, but you should still consult your doctor immediately. This can happen when the nervous system is affected.

If you’re just tired, take some time to rest, take things easy, and get enough sleep. Try to reduce stress.


More amoxicillin resources and information

This list may not describe all the potential side effects of amoxicillin. If you are experiencing any adverse effects of any drug that isn’t listed here, call your doctor for advice.

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