Bacteremia: What It Is, Why Bacteria Get Into Your Blood, and How Antibiotics Clear It
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD. Last reviewed October 17, 2026. This content is for educational purposes and is not medical advice.
Quick Answer
Bacteremia is the presence of bacteria in the blood, which is normally sterile, also called a bloodstream infection [1]. Bacteria usually enter through skin wounds, dental procedures, catheters or shared needles [1]. It often causes no symptoms, but fever, chills and low blood pressure can develop [1] [4]. Treatment is antibiotics [1] [4]; untreated, it can progress to sepsis and septic shock, which can be fatal [1].
What the research says
For uncomplicated gram-negative bacteremia, shorter antibiotic courses worked as well as longer ones. In a meta-analysis of 6 studies and 2,689 patients, short and long courses showed no significant difference in 30-day mortality (risk ratio 0.85, 95% CI 0.65 to 1.13) or 30-day recurrent bacteremia (risk ratio 1.07, 95% CI 0.68 to 1.67). The length of your own course depends on the infection, so follow the duration your provider sets (Li et al., J Clin Pharm Ther, 2021) [6].
The "shorter is better" idea is backed by over 120 trials across common infections. A review found that short antibiotic courses consistently gave similar treatment success to longer courses for conditions including gram-negative bacteremia, as long as the diagnosis was confirmed, the right antibiotic was used, and the patient was improving (Lee et al., Clin Microbiol Infect, 2023) [7].
What Is Bacteremia?
Bacteremia is when you have bacteria in your blood [1] [4]. Your blood is typically sterile, meaning it contains no bacteria or other germs [1]. So when bacteria show up in your bloodstream, something is off.
It can be helpful to think of your bloodstream as a highway system. Germs are normally kept out of it, but every day, tiny "on-ramps" exist. Bacteria can enter in many possible ways, but they typically slip in through skin wounds like cuts, scrapes, or burns [1].
Bacteremia goes by other names, too. You may hear it called a bloodstream infection (BSI) or blood poisoning [1]. These terms describe the same underlying situation: bacteria where they should not be.
Is Bacteremia Dangerous?
It depends on two things: how your immune system responds, and whether treatment happens early.
If you have a healthy immune system, your body usually removes the bacteria on its own, often without any symptoms at all [1]. But bacteremia can be a serious condition, especially in people with weak immune systems that struggle to fight off infections [1].
Without treatment, bacteremia can cause other infections to take hold elsewhere in your body. And in the worst cases, it can be fatal: untreated bacteremia can progress to sepsis, a whole-body reaction that can cause organ failure and death [1] [5].
Is Bacteremia the Same as Sepsis or Septicemia?
No, and the distinction matters.
Term | What it means |
Bacteremia | Bacteria are present in your bloodstream. Your immune system may clear them without symptoms. |
Septicemia | More serious than bacteremia. The bacteria in your blood are starting to multiply and spread to other areas of your body. |
Sepsis | Your immune system overreacts to the infection and attacks normal tissues and organs, causing body-wide inflammation. |
Untreated bacteremia can progress down this path: first septicemia, then sepsis. That progression is exactly why early treatment is so important.
What Are the Symptoms of Bacteremia?
Here is the surprising part: there are often no symptoms at all. When your immune system recognizes bacteria in your blood, it removes them from your body, usually without any symptoms or only a mild fever [1] [4].
If bacteremia progresses to sepsis or septic shock, however, symptoms become harder to ignore:
Chills
Fast heart rate (tachycardia)
Low blood pressure (hypotension)
Abdominal pain
Nausea and vomiting
Diarrhea
Rapid breathing (hyperventilation)
Symptom | What it looks like |
Chills | Shivering or feeling cold and shaky |
Tachycardia | A heart rate that beats faster than normal |
Hypotension | Blood pressure that drops lower than normal |
Abdominal pain | Pain in the belly area |
Nausea and vomiting | Feeling sick to your stomach, possibly throwing up |
Diarrhea | Loose, watery stools |
Rapid breathing | Breathing faster than normal (hyperventilation) |
Because mild bacteremia can be invisible, symptoms you can feel, especially those listed above, deserve attention rather than delay.
How Does Bacteria Get Into Your Blood?
Bacteria can get into your blood through cuts, burns, dental or medical procedures and shared needles, and many different kinds of bacteria can cause bacteremia [1]. Some examples include:
Bacillus cereus (B. cereus)
Escherichia coli (E. coli)
Pneumococcal bacteria
Salmonella
Staphylococcus aureus (staph), including methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA)
And yes, it is entirely possible that a routine part of your day, like brushing your teeth, is one of the ways bacteria find the door in.
Culprit bacteria | Examples |
Bacillus cereus (B. cereus) | A soil and food-associated bacterium |
Escherichia coli (E. coli) | One of the most common causes of bloodstream infection |
Pneumococcal bacteria | A cause of pneumonia and other infections |
Salmonella | A food-associated bacterium |
Staphylococcus aureus (staph) | Includes MRSA (resistant) and MSSA (susceptible) forms |
Which Bacteria Are the Most Common Culprits?
The most common bacterial causes of bloodstream infections are E. coli, Staphylococcus aureus, and Streptococcal species [1].
How Do Bacteria Get In?
These bacteria can enter your body in many different ways:
Scrapes
Cuts
Burns
Brushing or flossing your teeth too vigorously
Dental procedures, including teeth cleanings or a tooth extraction
Medical procedures, including surgery, catheterization, inserting breathing tubes, or blood donations
Reusing or sharing needles
The last three categories explain why bacteremia disproportionately affects people who are already in medical care: IV lines, catheters, and breathing tubes create direct paths past the skin, the body's main barrier. And the dental ones remind us that everyday hygiene habits have limits: gentle is better than aggressive.
What Complications Can Untreated Bacteremia Cause?
Untreated bacteremia can travel to other areas of the body and cause problems in the skin, heart, brain, bones, belly or lungs [1] [4].
Complication | What It Is |
Cellulitis | A skin infection |
Endocarditis | An infection of the heart's inner lining |
Meningitis | An infection of the tissues around the brain and spinal cord |
Osteomyelitis | A bone infection |
Peritonitis | An infection of the abdominal lining |
Pneumonia | A lung infection |
This is the domino effect that makes early treatment worthwhile: one bloodstream infection can seed trouble in the skin, heart, brain, bones, belly, or lungs.
How Is Bacteremia Diagnosed?
A healthcare provider can diagnose bacteremia. They will conduct a physical examination and ask about your symptoms, including how long you have had them [1].
If the provider suspects bacteremia, they will order tests to confirm the diagnosis. The workhorse is the bacteria culture: tests where samples of bodily fluids are checked for the presence of bacteria [1] [4].
Test | What happens |
Blood test | A thin needle withdraws a small amount of blood, usually from a vein in your arm |
Sputum test | You cough sputum (phlegm, the thick, discolored mucus from deep inside your lungs) into a special container |
Urine test (urinalysis) | You pee into a special container |
Wound culture | If you have an infected scrape, cut, burn, or abscess, the provider takes a sample of fluid or pus from your wound |
The provider may also order X-rays, a computed tomography (CT) scan, or an ultrasound to determine where an infection may be in your body [1].
How Is Bacteremia Treated?
Bacteremia is treated with antibiotics, and providers may also remove an infected medical device or drain an abscess [1] [4], with most people feeling better a few days after starting antibiotics [1].
Can Bacteremia Be Cured?
Yes, and speed matters. Getting treatment as soon as possible is important if you have signs of bacteremia. A healthcare provider will prescribe antibiotics to help treat the infection [1].
Beyond medication, treatment can also be mechanical:
The provider may remove any medical devices suspected of causing the bacteremia (such as an infected catheter).
If you have an abscess, they will drain the fluid and pus.
How Soon Will I Feel Better?
You should start to feel better a few days after starting antibiotics [1].
The Single Most Important Rule
Finish your full course of antibiotics, even if you start to feel better. This is not a suggestion; it is one of the most important steps in your recovery. If you do not take your full course of medicine, bacteremia may return [1]. And if bacteremia comes back, it may be more challenging to treat and more likely to develop into sepsis or septic shock.
If you miss a dose, take it as soon as you remember.
What Is the Outlook?
With early treatment, the outlook for bacteremia is good. Your body should clear the infection a week or two after you start taking antibiotics [1].
Without treatment, bacteremia may develop into a more serious condition. If you have signs of an infection, talk to a healthcare provider.
Can Bacteremia Be Prevented?
The best way to prevent bacteremia is to regularly wash your hands and clean any skin wounds [1]. Here is the wound-care sequence:
Clean any scrapes, cuts, or burns with antibacterial soap and water.
Pat your wound dry with a clean towel.
Apply a skincare ointment such as Neosporin or Aquaphor.
Cover it with a bandage.
Good hand hygiene is the foundation. Most of the entry routes listed above start with bacteria on hands, instruments, or skin surfaces that contact wounds.
How Do I Take Care of Myself?
Taking care of yourself with bacteremia means prioritizing your health and knowing when symptoms call for a healthcare provider or emergency care. Brief bacteremia from things like tooth brushing usually clears on its own, but bacteremia found on a blood test or causing symptoms needs the antibiotics your provider prescribes [1]. You can help take care of yourself by prioritizing your health and doing things like:
Getting at least seven hours of sleep each night
Drinking lots of water
Eating healthy foods, including lots of fruits and vegetables
When Should I See a Healthcare Provider?
See a healthcare provider if you have any symptoms of bacteremia, especially if your symptoms last more than a few days. Follow up with your provider if your symptoms don't go away a few days after starting treatment.
When Should I Go to the ER?
Go to the nearest emergency room if you have signs of sepsis, septic shock, or another serious infection, including [1] [5]:
A fever over 103 degrees Fahrenheit (39.4 degrees Celsius) or higher
Confusion or disorientation
Fast heart rate
Shortness of breath
Extreme pain or discomfort
What Questions Should I Ask My Healthcare Provider?
How did I get bacteremia?
What kind of bacteria caused bacteremia?
How do I avoid getting bacteremia in the future?
What antibiotic do you recommend?
Are there any special directions I need to follow while taking antibiotics?
How long will it take to feel better?
Do I need to schedule a follow-up appointment?
What can I do to help alleviate my symptoms at home?
Conclusion
Bacteremia sounds alarming, and in its worst forms, it genuinely is. But for most people, it is a story with a happy ending: bacteria slip in through a wound or procedure, the immune system does its job, and if needed, antibiotics clean up the rest within a week or two. The real risks come from waiting too long or quitting the antibiotics early. Wash your hands, treat your wounds properly, finish every prescribed pill, and know the warning signs that mean "go to the ER now."
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Frequently Asked Questions
What exactly is bacteremia?
Bacteremia is when bacteria are present in your blood. Blood is normally sterile, meaning it contains no bacteria or other germs. It is also called a bloodstream infection (BSI) or blood poisoning.
Is bacteremia common?
Bacteria can enter the bloodstream in many everyday ways, such as through cuts, scrapes, dental cleanings, or medical procedures. Often a healthy immune system clears the bacteria without you ever knowing, so mild, transient bacteremia may be more common than its name suggests.
Can bacteremia go away on its own?
Yes. If you have a healthy immune system, your body usually removes the bacteria from your blood without treatment, often without any symptoms or with only a mild fever. But bacteremia found on a blood test, or that causes fever and chills, needs prompt medical care and usually antibiotics.
Can bacteremia be fatal?
Yes, without treatment. Untreated bacteremia can progress to sepsis, which can cause organ failure and death. This is why early treatment matters so much.
What's the difference between bacteremia, septicemia, and sepsis?
Bacteremia is bacteria in your bloodstream. Septicemia means those bacteria are multiplying and starting to spread to other areas of your body; it is more serious than bacteremia. Sepsis is when your immune system overreacts to the infection and attacks normal tissues and organs, causing body-wide inflammation.
How do bacteria get into my blood?
Typically through skin wounds like cuts, scrapes, or burns. They can also enter through vigorous tooth brushing or flossing, dental procedures, surgery, catheterization, breathing tubes, blood donations, and reused or shared needles.
Can brushing my teeth really cause bacteremia?
Yes. Brushing or flossing too vigorously can allow bacteria to enter the bloodstream, along with dental procedures like teeth cleanings or tooth extractions.
Which bacteria most commonly cause bacteremia?
The most common causes of bloodstream infections are E. coli, Staphylococcus aureus (including MRSA and MSSA), and Streptococcal species.
What are the symptoms of bacteremia?
Often there are no symptoms at all, or just a mild fever. If it progresses to sepsis or septic shock, symptoms may include chills, fast heart rate, low blood pressure, abdominal pain, nausea, vomiting, diarrhea, and rapid breathing.
How is bacteremia diagnosed?
A provider performs a physical exam, reviews your symptoms, and orders bacteria culture tests, which may include a blood test, sputum test, urine test, and wound culture. X-rays, CT scans, or ultrasound may also be used to locate the infection.
How is bacteremia treated?
With antibiotics, prescribed as soon as possible. The provider may also remove any medical device suspected of causing the infection and drain any abscesses.
How long does recovery take?
You should start to feel better a few days after starting antibiotics, and with early treatment your body should clear the infection within a week or two.
Can I stop antibiotics once I feel better?
No. Finish the full course your provider prescribed, even if you feel better. Stopping early may cause bacteremia to return, and a recurrence may be harder to treat and more likely to progress to sepsis or septic shock.
When should I go to the emergency room?
Go to the nearest ER if you have signs of sepsis or a serious infection: fever over 103°F (39.4°C), confusion or disorientation, fast heart rate, shortness of breath, or extreme pain.
How can I prevent bacteremia?
Wash your hands regularly and clean any skin wounds properly: clean scrapes, cuts, and burns with antibacterial soap and water, pat dry with a clean towel, apply an ointment like Neosporin or Aquaphor, and cover with a bandage.
Related Reading
Sepsis: Complete Guide to Symptoms, Causes, Risks, and Treatment: how bacteremia can escalate into a body-wide emergency.
E. coli Infection: Symptoms, Causes, and Treatment: one of the most common bloodstream bacteria.
Staph Infections: Symptoms, Causes, Treatment, and Prevention — Complete Guide: the staph bacteria behind many bloodstream infections.
References
Cleveland Clinic. Bacteremia. Cleveland Clinic. Updated July 21, 2023. https://my.clevelandclinic.org/health/diseases/25151-bacteremia
Smith DA, et al. Bacteremia. In: StatPearls [Internet]. StatPearls Publishing. Last updated July 17, 2023. PMID 28723008. https://www.ncbi.nlm.nih.gov/books/NBK441979/
Austin ED, et al. Peripheral Intravenous Catheter Placement Is an Underrecognized Source of Staphylococcus aureus Bloodstream Infection. Open Forum Infect Dis. 2016;3(2):ofw072. PMID 27191005. https://doi.org/10.1093/ofid/ofw072
Bush LM, et al. Bacteremia. Merck Manual Professional Version. Updated July 2024. https://www.merckmanuals.com/professional/infectious-diseases/biology-of-infectious-disease/bacteremia
Centers for Disease Control and Prevention. About Sepsis. CDC. Updated August 17, 2026. https://www.cdc.gov/sepsis/about/index.html
Li X, et al. Short-course versus long-course antibiotic treatment in patients with uncomplicated gram-negative bacteremia: A systematic review and meta-analysis. J Clin Pharm Ther. 2021;46(1):173-180. PMID 32981149. https://doi.org/10.1111/jcpt.13277
Lee RA, et al. Short-course antibiotics for common infections: what do we know and where do we go from here? Clin Microbiol Infect. 2023;29(2):150-159. PMID 36075498. https://doi.org/10.1016/j.cmi.2022.08.024
Medical disclaimer
This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider with any questions about a medical condition. If you have signs of sepsis, such as fever over 103°F, confusion, fast heart rate, shortness of breath, or extreme pain, seek emergency medical care immediately.
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