Bacterial infections are treated with antibiotics, and the specific type, dose, and duration depend on where the infection is, which bacteria are causing it, and how severe it’s become. Most uncomplicated bacterial infections clear up within 3 to 10 days of antibiotic therapy. The key to effective treatment is getting the right antibiotic matched to the right bug, taking the full course, and knowing what to watch for if things aren’t improving.
How Doctors Identify a Bacterial Infection
Before prescribing anything, your doctor needs to confirm that bacteria are actually the problem. Many infections that send people searching for answers, like sore throats, sinus congestion, and bronchitis, are viral. Antibiotics do nothing against viruses, and taking them unnecessarily contributes to resistance.
The diagnosis often starts with your symptoms and a physical exam, but lab tests can sharpen the picture. Blood markers like C-reactive protein (CRP) and procalcitonin help distinguish bacterial infections from viral ones. A CRP level above roughly 15 mg/L or a procalcitonin level above 0.5 ng/mL raises suspicion for a bacterial cause. For skin infections, UTIs, or more serious illnesses, your doctor may order a culture, which grows the bacteria from a sample (urine, wound swab, blood) and identifies exactly what’s there. Culture results also reveal which antibiotics the bacteria respond to, which becomes critical if a first-line treatment isn’t working.
How Antibiotics Are Chosen
Not all antibiotics work the same way, and doctors don’t pick them at random. The World Health Organization classifies antibiotics into tiers based on how broadly they kill bacteria: narrow-spectrum drugs that target a small group of bacteria, moderate-spectrum drugs that cover more ground, and broad-spectrum drugs reserved for serious or hard-to-identify infections.
For a straightforward infection where the likely culprit is well known, narrow-spectrum antibiotics are the first choice. A simple strep throat, for instance, responds well to basic penicillin. A skin infection caused by staph bacteria might call for a first-generation drug like cephalexin. These targeted options cause fewer side effects and do less damage to the beneficial bacteria in your gut.
Broad-spectrum antibiotics come into play when the infection is severe, the bacteria haven’t been identified yet, or the patient isn’t responding to narrower treatment. These drugs cast a wider net, killing many types of bacteria at once. That power comes at a cost: more side effects, greater disruption to your gut microbiome, and a higher risk of breeding resistant bacteria. The general principle in modern medicine, called antibiotic stewardship, is to use the narrowest effective drug for the shortest effective time.
How Long Treatment Lasts
Treatment duration has shifted significantly in recent years. The old standard of 10-day antibiotic courses for many common infections is giving way to shorter regimens backed by newer evidence. For uncomplicated pneumonia, the American Academy of Pediatrics now recommends 5 days of treatment. Both the World Health Organization and the UK’s National Institute for Health and Care Excellence published updated guidelines in 2024 and 2025 supporting 3-to-5-day courses for similar infections.
Uncomplicated urinary tract infections in women are often treated in as few as 3 days. Skin and soft tissue infections typically need 5 to 7 days. More complicated infections, like those involving bone, heart valves, or deep abscesses, still require longer courses that can stretch to weeks.
The important thing is to finish whatever course your doctor prescribes. Stopping early because you feel better can leave behind the hardiest bacteria, giving them a chance to multiply and potentially resist the antibiotic next time. If you’re experiencing side effects that make it hard to continue, call your doctor rather than just quitting.
Common Side Effects and How to Handle Them
Antibiotics kill bacteria, and they aren’t perfectly selective. Along with the harmful bacteria causing your infection, they also wipe out beneficial bacteria throughout your body. This is why side effects are common and usually gut-related.
Diarrhea is the most frequent complaint, followed by nausea, stomach cramps, and bloating. Some people develop yeast infections because the loss of protective bacteria allows yeast to overgrow. Skin rashes and dizziness also occur with certain classes of antibiotics. Most of these side effects are mild and resolve once you finish the course.
To reduce nausea, take your antibiotics with food unless the label specifically says otherwise. For diarrhea, stay hydrated and eat bland, easy-to-digest meals. Yogurt and fermented foods can help, but targeted probiotics offer more consistent support.
Using Probiotics During Antibiotics
Probiotics can reduce the risk of antibiotic-associated diarrhea, but timing and strain matter. According to guidance from the International Scientific Association for Probiotics and Prebiotics, the best results come from starting probiotics as soon as possible, ideally within 1 to 2 days of beginning your antibiotic.
Because most bacterial probiotics are themselves sensitive to antibiotics, spacing them about 2 hours apart from your antibiotic dose helps keep the probiotic organisms alive long enough to work. Yeast-based probiotics aren’t affected by antibiotics at all, so timing is less critical with those.
Once you finish your antibiotic course, continuing the probiotic for another 7 to 14 days is a commonly tested strategy that gives your gut flora time to reestablish. Not every probiotic product on the shelf has clinical evidence behind it. Look for products that specify the exact strains and doses used in studies, rather than generic “probiotic blend” labels.
Why Antibiotic Resistance Matters to You
Antibiotic resistance is not an abstract public health problem. It directly affects whether your infection responds to treatment. The CDC reported in 2024 that six major types of resistant hospital-acquired infections increased by a combined 20% during the COVID-19 pandemic compared to pre-pandemic levels. Those resistant bacteria include MRSA, which resists standard staph treatments, and ESBL-producing bacteria, which resist many common antibiotics used for UTIs and abdominal infections.
Resistance develops when bacteria survive partial antibiotic exposure and pass on their survival traits. This happens at a population level through overuse in healthcare and agriculture, but it also happens at an individual level when people skip doses, stop courses early, or take leftover antibiotics without a prescription. Every unnecessary or incomplete course of antibiotics gives bacteria another chance to adapt.
On a more hopeful note, new antibiotics are still reaching the market. In 2025, the FDA approved gepotidacin for uncomplicated urinary tract infections and zoliflodacin for uncomplicated gonorrhea. Both represent new classes of drugs that work differently from existing antibiotics, giving doctors fresh options against resistant strains.
Signs That an Infection Is Getting Worse
Most bacterial infections improve noticeably within 48 to 72 hours of starting the right antibiotic. If you’re not feeling better by day three, or if you’re getting worse at any point, that’s a signal something needs to change. The antibiotic may not match the bacteria, the infection may be deeper than initially thought, or resistance could be a factor.
Certain symptoms signal that a localized infection has spread into the bloodstream, a dangerous condition called sepsis. Watch for:
- Confusion or disorientation that wasn’t there before
- Fever with shivering or feeling unusually cold
- Rapid heart rate or a weak, racing pulse
- Shortness of breath at rest
- Clammy or sweaty skin
- Extreme pain that seems out of proportion to the infection
Sepsis is a medical emergency. If you or someone you’re caring for develops a combination of these symptoms during a bacterial infection, get to an emergency room. Sepsis progresses fast, and early treatment with IV antibiotics and fluids dramatically improves outcomes. Hours matter.
What You Can Do at Home
Antibiotics do the heavy lifting, but your body’s immune system does real work alongside them. Supporting your recovery doesn’t require anything exotic. Stay hydrated, especially if you have a fever or diarrhea. Rest genuinely helps, because sleep is when your immune system is most active in clearing infections. Eat regular meals to maintain your energy and support gut health during antibiotic treatment.
For localized infections like skin wounds or minor abscesses, keeping the area clean and dry speeds healing. Warm compresses can help draw small skin infections to the surface. Over-the-counter pain relievers can manage fever and discomfort while the antibiotics take effect. Avoid alcohol during treatment, as it can worsen side effects like nausea and may interfere with how some antibiotics are processed.