Doxyday 100 mg is a tablet containing doxycycline 100 mg, a broad-spectrum antibiotic from the tetracycline group, made by Acron Pharmaceuticals. It is used to treat bacterial infections and should only be taken on a doctor advice.
Last reviewed: November 2026. General information only, not medical advice. Contents and strengths can differ by manufacturer and batch, so always check your pack and follow your doctor.
Quick Facts
| Brand | Doxyday (Acron Pharmaceuticals) |
| Form | Tablet 100 mg, strip of 10 (a capsule is also sold) |
| Active ingredient | Doxycycline 100 mg |
| Class | Tetracycline antibiotic |
| Prescription | Take only on a doctor prescription |
| Not for | Viral infections such as colds and flu |
Doxyday Composition
- Doxycycline (100 mg): a tetracycline antibiotic.
- Form and pack: tablet, strip of 10. Doxyday is also sold as a capsule, so check your pack.
What Is Doxyday Used For?
- Bacterial infections of the lungs, throat and airways
- Eye, skin and urinary tract infections
- Genital and intestinal infections, as decided by your doctor
- It does not work against viral infections such as colds and flu
How It Works
Doxycycline stops bacteria from making the proteins they need to grow and multiply, which lets the immune system clear the infection.
How to Take It
Take it exactly as your doctor prescribes, whole with a full glass of water, at a fixed time each day. Stay upright for a while after taking it to avoid irritating the food pipe. Finish the full course even if you feel better. If you miss a dose, take it when you remember unless the next dose is near, and never double up.
Possible Side Effects
Common side effects include:
- Nausea, vomiting or diarrhoea
- Loss of appetite
- Skin rash or itching
- Sensitivity to sunlight, so use sun protection
Seek medical help for a severe rash, swelling of the face, trouble swallowing, severe headache or vision changes, or severe or bloody diarrhoea.
Precautions and Who Should Be Careful
- Pregnancy and breastfeeding: doxycycline is generally avoided. Tell your doctor.
- Children under 8: it can permanently discolour developing teeth, so it is avoided in young children.
- Antacids, iron and calcium supplements: take them at least 2 hours apart from doxycycline.
- Alcohol: avoid it during treatment.
- Tell your doctor if you have liver or kidney problems, lupus, porphyria, or take oral retinoids.
- Do not take it for viral infections or without a prescription.
Key Points to Remember
- Antibiotics work only against bacteria. They do not treat viral infections.
- Take it with a full glass of water and stay upright afterwards.
- Protect your skin from the sun while taking it.
When to Contact a Doctor
- Severe or bloody diarrhoea
- A severe headache or vision changes
- Pain or difficulty when swallowing
- A rash, swelling of the face or breathing trouble
- No improvement after a few days of treatment
Practical Tips
- Stay upright for at least 30 minutes after taking it to avoid irritating the food pipe.
- Use sunscreen and cover up outdoors to prevent sunburn.
- Keep a gap of at least 2 hours from antacids, iron and calcium.
- Finish the course, and do not save leftover tablets for later.
Questions to Ask Your Doctor or Pharmacist
- Is my infection bacterial and do I need a test?
- How many days should I take it?
- Is it safe with my other medicines and supplements?
- What should I do if I miss a dose?
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Frequently Asked Questions
Is Doxyday an antibiotic?
Yes. It contains doxycycline, a tetracycline antibiotic.
Can I take Doxyday with milk?
Dairy products and calcium can reduce absorption. Take it with water and keep a gap from calcium, iron and antacids.
Can I stop when I feel better?
No. Complete the full course your doctor prescribed.
Can I use it in pregnancy?
Generally not. Ask your doctor.
Can I take Doxyday with food?
Taking it with food or a full glass of water can reduce stomach upset. Avoid taking it with milk or calcium products at the same time.
Does doxycycline make you sensitive to the sun?
Yes. It can cause sun sensitivity, so use sunscreen and cover up outdoors.
Further reading: MedlinePlus (NIH): Doxycycline
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