Of the 5 infections adults most often ask about, only 2 usually need antibiotics: strep throat confirmed by a rapid test, and a urinary tract infection. Sinus infections need them in a minority of cases, decided by a specific timing pattern rather than by mucus color. Acute bronchitis and the common cold do not need antibiotics at all, regardless of how long the cough lasts or what color the phlegm is.
TL;DR: Out of the 5 things adults ask me about most, only 2 usually need antibiotics. A urinary tract infection does. Strep throat does, once a rapid test says it is strep. A sinus infection needs them only sometimes, and the deciding factor is timing rather than the color of your mucus. Chest colds and head colds do not need them at all, no matter how long the cough drags on or how green the phlegm gets. Green mucus does not mean bacteria. If you got better and then got worse again around day 5 or 6, that pattern matters and is worth a message. So is trouble breathing, a fever that will not come down, or feeling worse instead of slowly better after a week.
Almost every week someone asks me some version of the same question, usually 6 or 7 days into feeling awful: is it time for antibiotics yet? It is a fair question, and the honest answer is that it depends on which of a handful of patterns you are in, and that the pattern is knowable.
What follows is the adult outpatient guidance, drawn from the Centers for Disease Control and Prevention's recommendations for these 5 conditions, put into plain language and matched to how Fishtown Medicine handles each one. It is written so you can figure out where you probably sit before you message me, and so a colleague at another practice can use it as-is.
Which Infections Need Antibiotics?
Only 2 of the 5 usually do. Here is the whole picture in one place.
| Condition | Usually needs antibiotics? | What decides it |
|---|---|---|
| Sinus infection | Sometimes, in a minority | The timing pattern: severe, persistent past 10 days, or worse after getting better |
| Acute bronchitis (chest cold) | No | Nothing about cough duration changes this |
| Common cold | No | At least 200 viruses cause it |
| Sore throat | Only if strep | A rapid test, since symptoms alone cannot tell |
| Urinary tract infection | Yes | Symptoms plus a urine dipstick |
The reason this matters beyond your own week: antibiotics carry side effects every time they are used, they disturb the gut bacteria that take months to recover, and each unnecessary course pushes resistance forward for everyone. The gut consequences are covered separately.
Do I Need Antibiotics for a Sinus Infection?
Most sinus infections do not need antibiotics, because 90 to 98% of them are viral, and even some of the bacterial ones resolve without treatment.
That is a large number, and it clashes with how most people have experienced sinus care. Sinusitis is common enough that roughly 1 in 8 adults reported being diagnosed with it in a single year, which came to more than 30 million diagnoses, and a great many of those visits ended in a prescription that changed nothing about how the illness went.
Three patterns point toward a bacterial infection worth treating:
- Severe from the start. A fever of 39°C (102°F) or higher together with thick discolored nasal discharge or facial pain, running 3 to 4 days.
- Persistent. Symptoms going past 10 days with no improvement at all.
- Worse after better. A viral cold that ran 5 to 6 days, started improving, and then turned around with new fever, daytime cough, or nasal discharge. This double-worsening pattern is the most useful of the 3, because a plain virus does not usually do that.
Two things that do not decide it: the color of your mucus, which turns yellow or green from your own immune cells rather than from bacteria, and a sinus X-ray, which is not routinely recommended and rarely changes the plan.
When treatment is warranted, amoxicillin or amoxicillin-clavulanate is first-line. Azithromycin is not recommended for sinusitis, because roughly 40% of Streptococcus pneumoniae is now resistant to it, which is why a Z-Pak so often fails here. For a penicillin allergy, doxycycline or a respiratory fluoroquinolone such as levofloxacin or moxifloxacin are the alternatives. For uncomplicated cases where you can reach me easily, watchful waiting with symptom treatment is a legitimate plan rather than a delay tactic.
Saline irrigation, intranasal steroids, short-course decongestants, and anti-inflammatory pain relief all help whether the cause is viral or bacterial. The fuller version is on the sinus infection page.
Do I Need Antibiotics for Bronchitis or a Cough That Will Not Quit?
Acute bronchitis does not need antibiotics, and that stays true regardless of how long the cough has lasted.
This is the one that surprises people most, and it is the single largest source of unnecessary antibiotic prescriptions in adult primary care. Cough is the most common symptom that brings adults to a primary care office, and acute bronchitis is the most common diagnosis those visits produce. The cough itself often runs 2 to 3 weeks, sometimes longer, and the length of it is not evidence of a bacterial infection. Neither is green or yellow phlegm.
The job at the visit is to make sure this is bronchitis rather than pneumonia, which is a different illness with a different answer. Pneumonia is uncommon in otherwise healthy adults when the pulse, breathing rate, temperature, and lung exam are all normal, so the things that raise concern are:
- Heart rate at or above 100 beats per minute
- Breathing rate at or above 24 breaths per minute
- Temperature at or above 38°C (100.4°F)
- Focal findings on listening to the lungs, such as a patch of consolidation, egophony, or altered fremitus
When those are absent, a chest X-ray is generally not needed either. When one or more is present, imaging and a different treatment conversation both make sense.
For the cough itself, dextromethorphan, a first-generation antihistamine such as diphenhydramine, and a decongestant such as phenylephrine are the usual options, and it is fair to say the evidence behind all of them is thin. The CDC list also includes codeine, and Fishtown Medicine does not prescribe it. We do not prescribe opioids of any kind, for any duration or indication, so dextromethorphan is the cough suppressant available here. That is a standing practice policy rather than a judgment about your cough.
If the cough is still going strong past 3 weeks, or if it comes with breathlessness, blood, weight loss, or drenching night sweats, that is a different evaluation. Post-viral cough, asthma that only shows up as cough, reflux, and post-nasal drip are the usual culprits, and a cough that outlasts the illness deserves a look rather than another antibiotic.
Do I Need Antibiotics for a Cold?
A common cold never needs antibiotics, because at least 200 different viruses cause it and none of them respond to an antibacterial drug.
Evidence-Based Treatment
Dr. Ash reviews the research - and applies it to your specific biology.
Colds are the third most frequent diagnosis in office visits, and most adults get 2 to 4 of them a year, which means a typical adult spends a few weeks of every year feeling like this. The symptom list runs through fever, cough, runny nose, congestion, post-nasal drip, sore throat, headache, and body aches, in various combinations.
For symptom relief, a decongestant such as pseudoephedrine paired with a first-generation antihistamine gives some short-term help with nasal symptoms and cough, and anti-inflammatory pain relievers help with the aches and the sore throat. Antihistamines on their own do not do much for a cold, intranasal steroids have not shown benefit for cold symptoms specifically, and opioids have no role here either.
The reason to message me during a cold is a change in trajectory rather than the cold itself: a fever that climbs after several days of improvement, shortness of breath, chest pain, confusion, or symptoms that are still worsening past a week.
Do I Need Antibiotics for a Sore Throat?
A sore throat needs antibiotics only when a rapid test confirms group A strep, which causes just 5 to 10% of adult sore throats.
The part that trips people up is that no combination of symptoms can settle this by eye. A very convincing-looking throat can be viral, and a mild one can be strep. What the clinical picture does is decide whether to test. The Centor criteria are the standard tool, awarding a point each for fever, tonsillar exudate, tender lymph nodes in the front of the neck, and the absence of cough. Two or more points means a rapid antigen detection test is worth doing. In adults, a negative rapid test generally ends the matter, and routine back-up throat cultures are not recommended.
A negative test means no antibiotics. That is the whole rule, and it holds even when someone feels terrible, because treating a viral sore throat with penicillin gives you the side effects and none of the benefit.
When the test is positive, amoxicillin or penicillin remain first-line, for a full 10 days with any of the oral beta-lactams. For a penicillin allergy, cephalexin, cefadroxil, clindamycin, or a macrolide are the alternatives, though resistance to azithromycin and clindamycin among group A strep is increasingly common, so those are less dependable than they used to be. The strep throat page covers testing options and why we treat strep at all.
Do I Need Antibiotics for a UTI?
A urinary tract infection does need antibiotics, and this is the clearest yes on the list.
Cystitis is among the most common infections in women and is usually caused by E. coli. The classic combination is burning with urination, going frequently in small amounts, and a sense of urgency that arrives suddenly. Blood in the urine and discomfort low in the belly show up less often. On a urine dipstick, nitrites and leukocyte esterase are the most accurate indicators.
For an uncomplicated infection in a healthy non-pregnant premenopausal woman, first-line options are nitrofurantoin, trimethoprim-sulfamethoxazole where local resistance runs under 20%, and fosfomycin. Fluoroquinolones such as ciprofloxacin are held back for situations where those other agents will not work, because their side effect profile is heavier and reserving them protects their usefulness. Pregnancy, kidney involvement, recurrent infection, and male patients all change the plan, and those are covered on the UTI page.
How Fishtown Medicine Handles This
In my practice, most of these get sorted out over messages rather than in a visit, because the deciding information is a timeline rather than an examination. What I want from you is how many days in you are, what the fever has done, and whether anything got better and then worse again. That last one carries more weight than almost anything else you can tell me.
Direct access changes the arithmetic here. A great deal of unnecessary antibiotic prescribing exists because the patient could not reach anyone, waited 6 days, took an afternoon off work to be seen, and neither they nor the clinician wanted that visit to end with nothing. When you can message me on day 2 and again on day 6, watchful waiting stops being a gamble and becomes a plan with a check-in built into it. If it turns bacterial, we treat it that day, and if you need to be seen, same-day sick visits cover it.
When antibiotics are the right call, I would rather give the right one for the full course than a broad one for a short one. And when a course is necessary, it is worth doing something deliberate about the gut afterward, since the disruption outlasts the prescription by months.
Key Takeaways
- Of the 5 conditions adults ask about most, only strep throat confirmed by a rapid test and a urinary tract infection reliably need antibiotics.
- Mucus color does not distinguish viral from bacterial infection anywhere on this list, and it drives a large share of unnecessary prescriptions.
- Sinus infections are 90 to 98% viral, and treatment is decided by 3 timing patterns rather than by how bad it feels.
- Acute bronchitis does not warrant antibiotics regardless of cough duration, and the job at the visit is ruling out pneumonia using pulse, breathing rate, temperature, and the lung exam.
- A negative rapid strep test means no antibiotics, and adults do not routinely need a back-up culture.
- Azithromycin is a poor choice for sinusitis at roughly 40% pneumococcal resistance, and it is losing ground against group A strep as well.
- Fishtown Medicine does not prescribe codeine or any other opioid, so dextromethorphan is the cough suppressant offered here.
- Watchful waiting works when you can reach your physician, which is the part most systems cannot supply.
Related at Fishtown Medicine
- Sinus Infection Treatment - the fuller sinusitis workup, dosing, and when to escalate
- Strep Throat Treatment - testing options and why strep gets treated at all
- UTI Treatment - first-line agents, pregnancy, and recurrent infection
- Antibiotics and Gut Health - what a course does to the microbiome and how to recover
- Same-Day Sick Visits - when this does need to be seen
- When Asthma Hides Behind Normal Lung Tests - one cause of a cough that outlasts the illness
Scientific References
- Centers for Disease Control and Prevention. "Outpatient Clinical Care for Adults." Antibiotic Prescribing and Use. Updated 2024.
- Chow AW, Benninger MS, Brook I, et al. "IDSA Clinical Practice Guideline for Acute Bacterial Rhinosinusitis in Children and Adults." Clinical Infectious Diseases. 2012;54(8):e72-e112.
- Harris AM, Hicks LA, Qaseem A. "Appropriate Antibiotic Use for Acute Respiratory Tract Infection in Adults: Advice for High-Value Care from the American College of Physicians and the Centers for Disease Control and Prevention." Annals of Internal Medicine. 2016;164(6):425-434.
- Shulman ST, Bisno AL, Clegg HW, et al. "Clinical Practice Guideline for the Diagnosis and Management of Group A Streptococcal Pharyngitis: 2012 Update by the Infectious Diseases Society of America." Clinical Infectious Diseases. 2012;55(10):e86-e102.
- Gupta K, Hooton TM, Naber KG, et al. "International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women." Clinical Infectious Diseases. 2011;52(5):e103-e120.
- Smith SM, Fahey T, Smucny J, Becker LA. "Antibiotics for acute bronchitis." Cochrane Database of Systematic Reviews. 2017;6:CD000245.
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