Antibiotics: When Needed, When Useless

Key takeaways

Antibiotics kill BACTERIA, not viruses. Per CDC, antibiotics do nothing for a cold, a runny nose, flu, most sore throats, or most bouts of bronchitis.
Thick, yellow or green mucus is NOT proof of bacteria — CDC says plainly that antibiotics still do not work. This is the most commonly reversed belief of all.
Three things never to do: take somebody else's medicine or what was left over from a previous course · stop or change the dose yourself once you feel better · buy them on hearsay and press a doctor to prescribe them.
The harm is real: per CDC, rash, nausea, diarrhoea, fungal infections; more seriously, C. diff infection and life-threatening allergy. In children, reactions to antibiotics are the commonest reason a child ends up in emergency care because of a medicine.
Resistance is your own business: per NHS, taking antibiotics when you do not need them can mean they stop working for you next time. But this article is NOT against antibiotics — CDC writes plainly that antibiotics save lives, and if a doctor has prescribed them, take them exactly as prescribed and do not leave the course unfinished.

The most important thing first: antibiotics kill bacteria, not viruses. Colds, flu, most sore throats and most coughs are viral — taking an antibiotic does nothing at all to the cause, while you still get the full set of side effects. In Vietnam this medicine can be bought without a prescription, so the decision sits with the patient.

Recognising it: does this illness need antibiotics?

The question most people ask is «which antibiotic should I take». The question that comes before it is «is this the kind of illness that needs one». Per CDC, antibiotics are only needed for certain bacterial infections — the table below follows CDC's community guidance.

Common illness	Antibiotics needed?
Strep throat · whooping cough · urinary tract infection	YES
Sinusitis · middle ear infection	MAYBE — the doctor decides
A cold, a runny nose · sore throat not caused by strep · flu	NO
Bronchitis in somebody previously well	NO

Where people go wrong

Thick, yellow or green mucus or phlegm: CDC says plainly that antibiotics do not work against a virus, EVEN WHEN the mucus has changed colour like that. Colour is not proof of bacteria.
A high fever: fever is a response to infection in general, viral infections included — on its own it does not tell you this is bacterial.

What to do when antibiotics are not needed

Ask a doctor or a pharmacist how to feel more comfortable while your body fights the virus off — per CDC, that is the question to ask instead of asking for antibiotics.
Rest properly and drink steadily; for a blocked nose, use saline drops. For fever or pain, ask a doctor or pharmacist: paracetamol (acetaminophen) is the usual choice, but the dose is theirs to decide.
Write things down before you go in: the date the illness started, the medicines you take, any history of drug allergy, whether you are pregnant or breastfeeding, and whether you have liver or kidney disease. Per NHS, some antibiotics are not suitable for people who are pregnant, breastfeeding or who have certain underlying conditions.

Three things never to do

DO NOT take somebody else's antibiotics, or what was left over from a previous course. CDC puts it directly: do not share them, do not save them for next time, do not take medicine prescribed for somebody else — doing so can delay the right treatment for you, make the illness worse, or cause side effects.
DO NOT stop or change the dose yourself once you feel better. Per CDC, if antibiotics are needed, take them EXACTLY as prescribed. Feeling better is a good sign, but it does not tell you the course is finished.
DO NOT buy them on hearsay, and do not press a doctor to prescribe them: CDC states explicitly never to pressure a qualified professional into prescribing antibiotics.

What you lose by taking them when you do not need them

Per CDC, the common side effects are rash, dizziness, nausea, diarrhoea and fungal infections; more serious are C. diff infection — a form of diarrhoea that can lead to severe damage to the colon and to death — and life-threatening allergic reactions. CDC states plainly that these can happen even when you did not need the medicine at all.
Resistance is not only society's problem: per NHS, taking antibiotics when you do not need them can mean they stop working FOR YOU next time. Resistant bacteria live in your body and in your household.

When antibiotics genuinely are needed

This is not an anti-antibiotic article: if you are holding a doctor's prescription, do not abandon the medicine after reading it. CDC writes plainly that antibiotics save lives, and that when they are genuinely needed the benefits outweigh the risks of side effects and of resistance. The question is WHO decides. Per CDC, the three questions to ask are:

What is the best way to treat this illness — are antibiotics needed?
If they are prescribed, what do I need to know about this medicine?
If antibiotics are not needed, which signs mean I have to come back?

When you must go to hospital

GO FOR EMERGENCY CARE NOW or call 115 (the emergency number in Vietnam) if, after taking the medicine, there are signs of a severe allergic reaction — NHS places this group among those needing emergency care immediately: difficulty breathing, wheezing, tightness in the throat or chest; swelling of the lips, face, tongue or throat; being unable to speak in full sentences; a rash with itching, swelling, blistering or peeling skin; blue lips or face; feeling faint, collapsing. Bring the medicine box with you. — BE SEEN THE SAME DAY, do not wait for the course to finish, if: there is heavy diarrhoea, abdominal pain or fever while taking antibiotics or just after the course — per CDC this can be C. diff infection, which needs treating; a rash, hives or marked itching; the illness is not improving or is getting worse despite the medicine; new tendon pain or muscle pain after starting the medicine.

When to call a doctor

What a family most needs here is usually not a box of medicine but somebody to read the prescription for them. A Y Te Xanh doctor visiting the home takes the history, examines the patient and says clearly which cases must be admitted; if nobody needs to come out yet, advice by video call comes first — exactly at the point when you have mild symptoms dragging on and are about to go to the pharmacy yourself.

Our medication review service goes through what you are currently taking: reading the prescription back to you, explaining what each item is for, and pointing out duplicated active ingredients or interactions worth worrying about. Two things we do NOT do: we do not sell medicines, and we do not change or stop a medicine on your behalf — where we see something questionable, we set it out clearly so that you can take it back to the prescribing doctor. If any sign in the box above is present, go in first and call afterwards.

The classification of which illnesses need antibiotics, the point about mucus colour, the side effects, C. diff infection and the things never to do all follow the community guidance of the US CDC; the signs of severe allergy, the notes on underlying conditions and pregnancy, and the point that the medicine may stop working for you personally all follow NHS. This article passes them on and does not replace being examined. Citing CDC does not imply that CDC endorses Y Te Xanh or our services.

Need personalised advice for your loved one? Call our hotline 094 368 81 15 (24/7) — calling to ask a question or to book costs nothing. GreenCare has doctors who come to examine, nurses who carry out doctor's orders (injections, infusions, dressing changes), remote consultation by video call, and a review of the medicines you are taking; an in-depth remote consultation, or any one after the first, is a paid service. For children we take examination and acute care only — not long-term care at home, and not newborns or expectant mothers. We confirm we have staff in your area and provide transparent pricing before we begin.

Sources

CDC — Antibiotic Prescribing and Use
NHS — Antibiotics

Frequently asked questions

I have had a cold, a cough and a fever for several days with no improvement — can I take antibiotics now?

The number of days without improvement is not grounds for switching to antibiotics. Per CDC, respiratory viruses usually clear up by themselves within one to two weeks without treatment, so not improving straight away is the ordinary course of a viral illness — and antibiotics do nothing to a virus. What is worth going on is the DIRECTION of travel, not the day count: CDC says that if an infection is not improving or is getting worse, you should be seen straight away. Difficulty breathing, chest pain, lethargy or being unable to drink mean going in, not counting more days at home.

The mucus or phlegm is green, yellow and thick — surely that means it is bacterial?

Not necessarily, and the two have to be separated. For NASAL MUCUS, CDC says it directly: antibiotics do not work against a virus, even when the mucus has turned thick, yellow or green — colour and thickness change as part of the natural course of a viral infection. For PHLEGM coughed up from the lungs it is different: the colour of phlegm can be a reason to be seen, but it has never been a reason to buy antibiotics yourself; this site has a separate article on a cough with phlegm. In either case, if you are holding a box of medicine and wondering, take the patient to be seen, or send a photograph of the prescription for a doctor to look at first, rather than trying it and waiting.

How long do I take antibiotics for, and can I stop once I feel well?

There is no single figure, because it depends on the kind of infection and on the patient — which is why the answer sits in your doctor's prescription and not in an article. The principle is clear enough: per CDC, if antibiotics are needed, take them exactly as prescribed. Feeling better is a good sign, but it does not tell you the course is finished. If you want to stop because of a side effect, phone the doctor or pharmacist and let them decide; do not stop on your own, and do not keep what is left for next time.

There is medicine left over from a previous course in the house — can I finish it rather than throwing it away?

You should not, and CDC places exactly this among the things not to do: do not share antibiotics with others, do not save them for next time, do not take medicine prescribed for somebody else. On top of that, what is left over is almost never enough for a full course, so it neither treats the present illness nor does anything except give bacteria an opening to become resistant. If you no longer need a medicine, take it to a pharmacy and ask how to dispose of it rather than leaving it in a cupboard for next time.

Resistance is a long-term problem for society — what has it got to do with me now?

It has everything to do with you. NHS puts it briefly: taking antibiotics when you do not need them can mean they stop working for you in the future. Resistant bacteria are not somewhere far away — they live in your body and in your household, so the next time you or a relative genuinely need the medicine, the remaining options may be fewer and harder. The right question is therefore not «is it safe to take this» but «do I really need to take this».

Is there anything particular to watch when a child takes antibiotics?

There is one figure worth knowing: per CDC, reactions to antibiotics are the commonest reason a child ends up in an emergency department because of a medicine; and reactions to antibiotics account for one in five emergency department visits for medicine-related problems across all ages. So with a child, the question «does she really need an antibiotic» matters even more than it does for an adult. CDC also notes that children can get better without antibiotics, and that the thing to do is ask the doctor how to help the child feel more comfortable while the body fights the virus off. Never divide an adult's medicine up for a child, and never reuse another child's old prescription — a child's dose is the doctor's business.