It's no secret that antibiotics are an incredible and often life-saving innovation. These powerful, fast-acting drugs fight unfriendly bacteria that cause infections. But do they have a dark side? Current research suggests they do.

Since antibiotics kill both beneficial and harmful bacteria, they can significantly damage the gut microbiome, potentially leading to chronic illness. And overuse of antibiotics can create drug-resistant superbugs that are a global health concern.  

The upside is that we can support the microbiome during and after antibiotic use with tools like diet, lifestyle, and the right probiotics to offset their long-term negative effects. In this post, we’ll:

• Walk through the major changes antibiotics cause in your microbiome
• Demystify how long it takes to restore good bacteria after antibiotics
• Cover how to restore gut health after antibiotics
• Help you decide if you should test your gut after antibiotics

Understanding the impact of antibiotic use and recovery

When we take antibiotics for an infection, our gut microbiome goes through phases. First, antibiotics attack gut bacteria. This results in a gut microbiome that is imbalanced with bad bacteria, followed by a sometimes-long journey back to a balanced, healthy gut. Let's explore these phases in more depth.

Phase 1: Antibiotics attack gut bacteria

Antibiotics don't distinguish between good and bad microbes. That’s why when you take an antibiotic, the amount and different types of bacteria in your gut—that is, the richness and diversity of your gut microbiome—decrease significantly [1]–[4].

Some species may even disappear, either temporarily or permanently [1], [2].

The drop in richness and diversity depends on different variables. For example, broad-spectrum antibiotics (e.g., ciprofloxacin, cefadroxil) target a wide range of bacteria and have a big impact. Narrow-spectrum antibiotics (e.g., metronidazole, erythromycin) target only a few types of bacteria.

Another important factor is the gut microbiome itself, which varies considerably person to person [5]. And that variation shapes the extent of disruption. One study found that with a 5-day course of antibiotics, most people lost around 10 species, while a few lost around 24 [1].

Phase 2: Rise in unfriendly bacteria

When it comes to your gut, balance is key.

Almost everybody has a small amount of unfriendly bacteria in their microbiome. And that’s okay. Beneficial bacteria keep these not-so-welcome tenants from taking up too much space.

The problem is, antibiotics can cause a significant drop in microbial diversity, disrupting a balanced gut [1]–[3].

During this phase, a specific group of microbes, drug-resistant bacteria, takes advantage of the decrease in protective bacteria to grow unchecked. 

Studies have shown that after antibiotics, the number of drug-resistant bacteria and the amount of antibiotic resistance genes increase [1], [2], [4], [6]. Our Tiny Health Gut Test looks at these bacteria and calculates your antibiotic resistance signature.

Your antibiotic resistance signature can help us track the long-term side effects of antibiotics. 

For some people, one of the unfriendly drug-resistant bacteria that may overgrow is Clostridioides difficile. If it's present in your gut, it can cause antibiotic-associated diarrhea [7]–[9].

Phase 3: The journey back to baseline

Some weeks after a course of antibiotics, beneficial bacteria repopulate your gut, putting unfriendly bugs in check [2].

But this process can be slow.

And how long it takes for gut bacteria to recover after antibiotics varies from person to person.

For most, the composition of the gut returns to baseline within 1 to 2 months. But for a few, it may take much longer. This is typically when we see the long-term effects of antibiotic use.

One study found that six months after antibiotics, some individuals only recovered about 63% of the bacterial species they had before the antibiotic treatment [1]. In another, friendly species such as Bifidobacterium, Coprococcus, and Eubacterium disappeared completely. And remained undetected from all participants at 6 months post-treatment [2].

Scientists are still not entirely sure why people respond differently to antibiotics. Some important factors to consider:

• The initial composition of the gut microbiome, which varies among individuals [5]
• An adult gut microbiome with low diversity to begin with
• A history of antibiotic use, from which the gut didn't fully recover

4 ways to replenish good bacteria after antibiotics

It may feel overwhelming to restore good bacteria after antibiotics, but the best place to start is with diet.

Eating the right foods can promote gut diversity while boosting the growth of beneficial bacteria.

To restore gut health after antibiotics, try:

1. Eating more foods high in fiber and/or polyphenols: This includes fruits, vegetables, nuts, legumes, and whole grains. These act as fuel for beneficial microbes and help them regrow.

2. Adding more fermented foods to your diet: These include yogurt, kefir, sauerkraut, kombucha, and kimchi. Fermented foods can introduce beneficial live microbes and support a more balanced ecosystem.

3. Eating a diverse diet: Aim for 30 different plant foods per week. Diversity in your diet supports diversity in your microbiome.

4. Limiting ultra-processed foods: These often contain excess saturated fats, sugars, and emulsifiers that contribute to gut imbalances and weaken your gut barrier.

How long does it take to restore gut health?

The timeframe is different for everyone, but here’s a general pattern.

Within 1 to 2 weeks

The acute disruption begins to settle. Some beneficial bacteria start to reestablish, and the initial drop in diversity starts to level off.

By 1 to 2 months

Most people return close to their pre-antibiotic baseline. Diversity improves, and opportunistic bacteria are brought back into check.

6+ months

A smaller group of people may still be working toward a full recovery. Factors like antibiotic type, prior antibiotic use, and gut diversity all influence recovery time.

‍

Can you take probiotics and antibiotics at the same time?

Yes. In fact, doing so during and after antibiotic treatment can help protect against infection caused by the overgrowth of drug-resistant bacteria like C. difficile [10]–[12]. It’s important to note that if you have suffered from a C. difficile infection in the past, you are at higher risk of a recurrent infection when taking a new course of antibiotics [13]. In such cases, we strongly recommend taking probiotics to support the restoration of the gut microbiome.

Another case in which we strongly recommend taking probiotics along with antibiotics is in babies who have gone through previous courses of antibiotics. Studies have shown that each new course of antibiotics adds to the risk of developing a chronic immune-mediated disease such as asthma and eczema [14]–[17].

How do I know if my gut has recovered after antibiotics?

In this article, we’ve covered the three phases of impact antibiotics have on your gut, and how to restore microbiome health after antibiotics. It may take some time for good bacteria to repopulate the gut, but the first step is trusting in your body's ability to heal. The second is taking action with a plan and expert guidance.

You can do this with Tiny Health gut microbiome tests, which:

• Give you the ability to detect antibiotic-resistant species
• Help you gauge responsiveness to antibiotics in the future
• Show whether you still need probiotic support
• Reveal any antibiotic signatures that are linked to an increased risk of developing eczema or allergies during pregnancy and a baby’s first year 

Testing your gut after antibiotics will help you make informed decisions about your recovery.

Interested in taking control of your family’s microbiome health and reducing the likelihood of future illness? With Tiny Health’s tests for babies, children, and adults, we teach you about your microbiome and give you unbiased recommendations to put your family on the path to better lifelong health.

‍