How to Take Antibiotics Correctly

Taken incorrectly, antibiotics can do more harm than good

Antibiotics are effective against bacterial infections, but used the wrong way they can breed antibiotic-resistant bacteria or trigger serious side effects. Knowing how to take them correctly matters.

The basics of how antibiotics work

What is an antibiotic?

A drug that kills bacteria or stops them from growing
→ Has no effect on viruses

Viral illnesses (antibiotics NOT needed):
- Common cold (mostly viral)
- Flu (influenza virus)
- COVID-19
- Most cases of simple gastroenteritis

Bacterial infections that need antibiotics

Situations where antibiotics are needed

Bacterial pneumonia
Urinary tract infections (cystitis, pyelonephritis)
Bacterial tonsillitis and otitis media
Cellulitis
Tuberculosis
STIs (gonorrhea, syphilis) → Always take only after a doctor’s prescription

Major classes of antibiotics

Class	Representative drugs	Main uses
Penicillins	Amoxicillin	Tonsillitis, otitis media, UTIs
Cephalosporins	Cefaclor, cefadroxil	Skin infections, UTIs
Macrolides	Azithromycin (Zithromax)	Pneumonia, STIs, skin infections
Fluoroquinolones	Ciprofloxacin	Severe UTIs, pneumonia
Tetracyclines	Doxycycline	Acne, malaria prevention, STIs
Metronidazole	Flagyl	Anaerobic infections, vaginal infections

Rule 1: Finish the entire prescribed course

Keep taking antibiotics until the full course is done, even if symptoms improve
Why:

Feeling better ≠ the bacteria are fully cleared
Stopping early → surviving bacteria multiply → relapse + resistance

Example

7-day course for tonsillitis
Symptoms improve after 3 days → tempted to stop → Never do this → complete the full 7 days

Rule 2: Keep the dosing interval consistent

Twice-daily dosing: every 12 hours

Three-times-daily dosing: every 8 hours

Keeps blood drug levels steady
If levels drop, surviving bacteria can regrow

Rule 3: How food interacts with antibiotics

Take on an empty stomach: ampicillin, some fluoroquinolones
Take with food: amoxicillin, cefadroxil

Foods to watch

Dairy: don’t take with tetracyclines/fluoroquinolones (blocks absorption)
Alcohol: never mix with metronidazole (causes severe headache, vomiting)
Grapefruit juice: can abnormally alter blood levels of some antibiotics

Antibiotic side effects and how to handle them

Common side effects

GI upset (most common):

Symptoms: nausea, vomiting, diarrhea, stomach pain
Management: take with food, pair with probiotics

Antibiotic-associated diarrhea (AAD):

Cause: disruption of normal gut flora
Management: take a probiotic supplement (2 hours after the antibiotic dose)

Vaginal or oral yeast infections (candidiasis):

Cause: antibiotics reduce normal bacteria → yeast (Candida) overgrows
Management: ask your doctor about adding an antifungal

Serious allergic reactions (seek emergency care immediately)

Warning signs:

Full-body hives + difficulty breathing → anaphylaxis (emergency)
Rash spreading across the whole body
Swelling around the mouth or eyes
Fever accompanied by rash

Emergency steps:

Call emergency services or go to the ER immediately
Stop taking the drug
Bring the prescription packaging with you

Antibiotic resistance: why it’s such a serious problem

How resistance develops

Antibiotic use

Bacteria that happen to tolerate the drug survive
Resistant bacteria multiply
The same antibiotic no longer works
A stronger antibiotic is needed → repeat → superbugs emerge

Rules for preventing resistance

Complete the full prescribed course
Never take antibiotics without a doctor’s direction
Don’t save leftover antibiotics for later use

Don’t

Borrow antibiotics from friends or family
Ask for antibiotics for a cold “just in case”
Buy antibiotics online without a prescription

Precautions for children

Weight-based dosing matters:

Never cut an adult tablet in half for a child
Always use a pediatric liquid formulation or a pediatrician’s prescription

Rash after taking an antibiotic:

Contact a doctor immediately (need to distinguish an allergy from a drug rash)

Don’t push for unnecessary antibiotics:

Requesting antibiotics “just in case” for a cold does more harm than good

Antibiotics during pregnancy

Antibiotics generally considered safe in pregnancy (Category B):
- Amoxicillin
- Most cephalosporins
- Erythromycin (some formulations)

Antibiotics to avoid during pregnancy:
- Tetracyclines: affect fetal bone and tooth development
- Fluoroquinolones: affect fetal joint development
- Metronidazole: contraindicated in early pregnancy (2nd/3rd trimester at a doctor's discretion)

→ Always tell your doctor you're pregnant before getting a prescription

Frequently asked questions

Q. Can I ask for antibiotics for a cold? A. A common cold is viral, so antibiotics won’t help. Taking them anyway only raises your risk of resistant bacteria and side effects. Follow your doctor’s judgment.

Q. What happens if I drink alcohol while on antibiotics? A. Metronidazole reacts with alcohol and can cause severe headaches and vomiting. Even with other antibiotics, drinking is best avoided since it weakens immunity and slows recovery.

Q. Can I use leftover antibiotics later? A. No. Antibiotic prescriptions depend on the type of infection and the specific bacteria involved. A drug prescribed for a past infection may not be right for a new one, and reusing it raises the risk of resistance.