Tetracycline vs Doxycycline – A Complete Overview

With all the antibiotics available to treat infections, it can be challenging to tell the difference between different types. This is especially true for antibiotics within the same medication class, such as tetracycline and doxycycline.

Being in the same class, these two antibiotics function similarly, but they work on different types of infections and may cause some different side effects.

Continue reading for a complete comparison between tetracycline and doxycycline.

Table of Contents

Are Tetracycline and Doxycycline Hyclate the Same Thing?

Tetracycline and doxycycline are both antibiotics belonging to the tetracycline antibiotic class. Despite this, though, they are not the same thing.

Doxycycline is a derivative of tetracycline, so while it is similar, its structure is still different, allowing it to treat different types of bacterial infections.

What Is Tetracycline?

Tetracycline is a type of antibiotic that treats bacterial infections, and it belongs to the class of medications called tetracycline antibiotics. It stops bacteria by preventing them from making specific proteins, which stops the bacteria from multiplying and spreading.

Some of the conditions that tetracycline can treat include:

  • severe acne
  • bacterial skin infections
  • urinary tract infections (UTIs)
  • chlamydia
  • chancroid
  • gonorrhea
  • syphilis
  • Rickettsia infections (e.g., typhus fever and Rocky Mountain spotted fever)
  • plaque
  • anthrax
  • cholera

What Is Doxycycline?

Doxycycline is another antibiotic that also belongs to the class of tetracycline antibiotics. In addition to treating bacterial infections, though, it is also able to reduce the inflammation that results from the condition of rosacea.

Doxycycline inhibits bacteria by attaching to their ribosomal subunits. When it does this, the bacteria are unable to link together amino acids, which are the building blocks of proteins. When the bacteria’s proteins are unable to be synthesized, the bacteria cannot function and eventually die.

Some of the infections that doxycycline is used to treat include:

  • respiratory tract infections (from Streptococcus pneumoniae, Haemophilus influenzae, or Mycoplasma pneumoniae)
  • non-gonococcal urethritis
  • anthrax
  • typhus
  • chancroid
  • brucellosis
  • syphilis
  • cholera
  • Rocky Mountain spotted fever
  • Acne
  • periodontal disease
  • rosacea
  • urinary tract infections
  • gonorrhea
  • actinomycosis
  • chlamydia
  • Lyme disease
  • Vincent’s infection

Doxycycline can also be used as a preventative treatment for malaria.

Tetracycline vs. Doxycycline

Listed below is a complete comparison between tetracycline and doxycycline. 

How Are Doxycycline and Tetracycline Different?

Doxycycline is an antibiotic derived from tetracycline, which is why they are both tetracycline antibiotics. This means that they have many similarities in their structure, although the fact that they are slightly different does lead to differences in the illnesses they can treat.

Additionally, doxycycline is absorbed faster (and better) by the body, and produces peak serum concentrations faster than tetracycline. This means that doxycycline starts fighting the infection faster than tetracycline. 

Doxycycline vs. Tetracycline Side Effects

Like all antibiotics, tetracycline and doxycycline share some side effects, which revolve around an upset stomach and can include nausea, vomiting, and diarrhea.

As for each medication, some of the common side effects of doxycycline can include:

  • weight loss
  • rash
  • hives
  • anemia
  • vaginal yeast infection

Some side effects specific to tetracycline include:

  • headache
  • rash
  • dizziness

Tetracycline and doxycycline can also cause tooth discoloration if used by someone younger than 8.

Dosage of Tetracycline vs. Doxycycline

Tetracycline comes as a capsule that is taken by mouth between two (500 mg doses) to four (250 mg doses) times a day. Tetracycline must be taken on an empty stomach and should be taken one hour before meals or snacks or two hours after. When taking tetracycline, take it with a full glass of water.

Dairy products, in particular, can reduce the absorption of tetracycline. Hence, it is important to avoid taking it with these products or within a certain amount of time since they were eaten.

For most infections, the length of time tetracycline is prescribed can vary between 7 to 14 days, depending on the infection it is treating.

Doxycycline is offered in multiple forms, including a capsule, tablet, delayed-release tablet, and liquid suspension. For those taking doxycycline in liquid form, the medicine must be thoroughly mixed before taking it.

The typical dose of doxycycline is 200 mg on the first day (100 mg every 12 hours), and then the dose can range from 100 mg to 200 mg each day following. It may be taken once or twice a day, and the complete course typically lasts 7 to 14 days.

Compared to tetracycline, doxycycline may be taken with food if it causes an upset stomach.

No matter which antibiotic you are prescribed, it is essential to follow your doctor’s instructions in regard to how long it must be taken. Taking the antibiotic for too long or too little can increase the risk of antibiotic resistance, which can lead to a more severe infection.

Warnings of Tetracycline and Doxycycline

There are some medical conditions that can negatively interact with both tetracycline and doxycycline, such as hepatotoxicity, colitis, and esophageal irritation. In addition, tetracycline can also interact with renal dysfunction.

Doxycycline and tetracycline are also known to increase skin sensitivity to the sun. To protect yourself, try to avoid extended periods of time in the sun while taking them. When you do go outside, opt for protective clothing, and don’t forget your sunglasses and sunscreen.

It is not safe for pregnant women to take tetracycline or doxycycline, as they can both cross the placenta and affect the fetus’s bone development. If you become pregnant while taking doxycycline or tetracycline, discontinue the antibiotic immediately and talk to your healthcare provider about another type of treatment.

These health effects can also be passed to a child through breast milk, so breastfeeding mothers should avoid taking these antibiotics to protect their child’s health.

Drug Interactions of Tetracycline and Doxycycline

Tetracycline and doxycycline have some similar medications which they may interact with, including:

  • penicillin
  • anticoagulants
  • antacids (containing calcium, aluminum, or magnesium)
  • iron-containing preparations
  • oral contraceptives
  • methoxyflurane

There are also some medications which doxycycline alone may interact with, which can include:

  • bismuth subsalicylate
  • carbamazepine
  • phenytoin

Doxycycline may also enhance the effect of warfarin, which can cause excessive blood thinning.

Because of the potential for drug interactions, discussing with your doctor any medications or supplements you already take when being prescribed an antibiotic is essential.

Which Is Better, Tetracycline or Doxycycline?

Because tetracycline and doxycycline can treat many of the same infections, one consideration that might impact which medication would be best for you is how many daily doses you will need. Tetracycline may require four doses a day, so if that may be hard to adhere to, it is likely best to go with doxycycline since it typically requires only one or two doses a day.

The many forms of doxycycline may also be preferable, such as the liquid form which may be easier for some people to take.

A 2017 study also found that doxycycline is potentially less damaging to the liver than tetracycline, making it a potentially safer substitute.

Additionally, there are an increasing number of reports of antibiotic resistance to tetracycline, which might make doxycycline a better choice for those with a history of antibiotic resistance or recurrent infections. 

However, substituting doxycycline for tetracycline is only an option if the infection is something that both medications treat. There are some infections specific to each drug, and in these cases treating with the other medicine would not produce beneficial results.

When to See a Doctor?

It is recommended to see a doctor as soon as you suspect you have an infection. Since bacterial infections often need antibiotics in order to be treated, visiting a doctor allows the bacteria longer to infect your body, which could lead to more serious conditions.

Taking an antibiotic that was not prescribed to you is never recommended, and doing so may result in dangerous scenarios or may lead to a reduction in antibiotic effectiveness. It is always best to discuss taking an antibiotic with your doctor so that they can weigh any health conditions and other medications.

Get Help From an Online Doctor

If you think you have an infection, an online doctor is an excellent resource to discuss your symptoms. With DrHouse, you can meet with a doctor in just 15 minutes to receive a diagnosis and prescription, all without having to leave the house.

Your online doctor can also discuss the differences between tetracycline and doxycycline with you and which antibiotic they feel is best for your specific scenario.

Key Takeaways

Tetracycline and doxycycline are two medications under the class of tetracycline antibiotics. They both work by inhibiting bacteria’s production of proteins, which then causes the bacteria to be unable to function.

Despite the similarities between these two medications, their structures have some differences, affecting the infections they can treat. Additionally, doxycycline is sometimes used as a prevention for malaria, while tetracycline is not.

There are many medications and health conditions that must be taken into consideration before taking either of these drugs. To ensure your safety, it is always recommended to discuss taking an antibiotic with your doctor. For those looking for a more convenient way of doing this, online doctors allow you to meet with a doctor and receive a prescription without having to leave your house.


Content on the DrHouse website is written by our medical content team and reviewed by qualified MDs, PhDs, NPs, and PharmDs. We follow strict content creation guidelines to ensure accurate medical information. However, this content is for informational purposes only and not a substitute for professional medical advice, diagnosis, or treatment. For more information read our medical disclaimer.

Always consult with your physician or other qualified health providers about medical concerns. Never disregard professional medical advice or delay seeking it based on what you read on this website.

If you are experiencing high fever (>103F/39.4C), shortness of breath, difficulty breathing, chest pain, heart palpitations, abnormal bruising, abnormal bleeding, extreme fatigue, dizziness, new weakness or paralysis, difficulty with speech, confusion, extreme pain in any body part, or inability to remain hydrated or keep down fluids or feel you may have any other life-threatening condition, please go to the emergency department or call 911 immediately.



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