Written by: Jennifer Chesak, MSJ
Medically reviewed by: Adam Perlman, MD, MPH and Taylor Berggren, MS, RDN
Probiotics are live microorganisms that have beneficial effects on your body. You can ingest them through food and supplements. Once in your gut, probiotics have multiple beneficial effects, improving both your gut health and overall health. You can monitor yourself for a variety of signs probiotics are working, including reduced gastrointestinal symptoms and improved health metrics, sleep, and mental health.
The human body fascinates me. We have a whole microbiota, a community of bacteria and fungi living in our guts. This microbiota impacts many aspects of our mental and physical health. I’m a health-conscious person, so I’m constantly on the hunt for health-habit changes that will support my gut, including probiotics.
“When we say ‘gut microbiome,’ we really are referring to the community of trillions of microbes, in particular bacteria, that live in our gut and are important for health,” says Colleen Cutcliffe, PhD, Co-Founder and CEO of Pendulum Therapeutics.
“These bacteria are important for digestion, metabolism, immunity, and more,” she adds. “Some people have lost key bacteria over time through things like antibiotics, diet, aging, etc. And the goal of supplementing with probiotic pills (or foods) is to reestablish those key microbes so you can have a fully functioning microbiome.”
That makes good sense to me, but I don’t just take something new without doing research beforehand and then assessing the results after a trial period.
If you’ve been trying a new supplement, you may also be looking for signs probiotics are working. How do you know your probiotics are doing good things for your body? Plus, how long does it take for probiotics to work? And what are the signs they may not be working? I’ve turned to the research to answer these questions and more.
What are probiotics and why take them?
“Probiotics are part of the world of the microbiome,” Dr. Cutcliffe says, “which we now know plays a huge role in our health. The shelves are lined with different products, so I think a quick 101 is always helpful. Probiotics are the live strains—usually we’re talking about bacteria—that live in our guts, on our skin, and all over our body that help us.”
Bacteria and yeast live in the gut as probiotics, which first seed the gut microbiome during transmission from mother to baby during infancy. After this early period of probiotic seeding, we can also take probiotics as oral supplements or ingest them via foods such as yogurt and kimchi. Fiber-rich foods can also serve as prebiotics, which feed the beneficial bacteria living in the gut, Cutcliffe explains.
Probiotic strains include the genus and species names (and sometimes a subspecies). Some of the most common probiotic genus names include:
- Lactobacillus
- Bifidobacterium
- Saccharomyces
- Enterococcus
- Bacillus
- Escherichia
- Streptococcus
Probiotics help your body in several ways. The mechanisms depend on the strain, but here are a few key benefits:
- Boost gastrointestinal health
- Help produce other substances that regulate hormones, blood sugar, and appetite
- Support the immune system
- Support the nervous system and mental health
How long does it take for probiotics to work?
You might notice changes related to taking probiotics in as little as one day or as long as several months.
“Every person is unique and experiences improvements at different times and to varying degrees,” Dr. Cutcliffe says. “You may have noticed this in other places too. Some people seem to be able to go on a diet or change their exercise regimen and immediately lose weight. And for others, [maintaining a healthy weight] is a real struggle.”
What’s behind these differences? “One key to this could be that the people who are struggling are missing key gut microbes that help them digest food and boost their metabolism,” she explains. “If you are seriously depleted in these you might experience changes in a matter of days.”
For others, the process may take more time. “If your microbiome ecosystem makes it more challenging for these probiotics to colonize,” Dr. Cutcliffe says, “we’ve seen it take even six months for people to experience a change. So it’s really a range.”
For acute issues, such as diarrhea, the right probiotic strain might produce results in about a day, according to research. For other issues, you might not experience results for several weeks or even months.
The amount of time required to experience a change will also depend on the type of change you are looking to see. For example, in one study on a five-strain probiotic, the researchers looked at changes to hemoglobin A1C (HbA1c). Because HbA1c is a test reflecting your average blood sugar over the past three months, you would need to take the probiotic for at least three months to assess results.
The study, published in the peer-reviewed journal BMJ Open Diabetes Research & Care, showed that in people with type 2 diabetes, the product lowered HbA1c significantly when compared with the placebo group.
Clear signs your probiotics are working
How well your body is metabolizing sugar is just one way you might notice that your probiotic is working over time. Here’s a closer look at that, and other signs to look for after starting probiotics. You may wish to track most symptoms—digestion, mood, sleep, etc.—in a journal (or a health app).
Improved digestive health
The first thing people usually notice with Pendulum probiotics is that their digestion improves, Dr. Cutcliffe says. You may experience a reduction in frequency or severity of diarrhea, constipation, gas, and bloating. Then once your digestion improves, you may start to see your metabolism improve. You may notice you have more energy throughout the day with fewer food cravings, Dr. Cutcliffe adds.
Probiotics increase the beneficial microbes in your gastrointestinal tract. This increased population helps prevent problematic microbes from overpopulating your gut. A healthier gut microbiome can result in improved nutrient absorption and a reduction in frequency or severity of gastrointestinal symptoms, such as constipation, diarrhea, bloating, distention, gas, and more.
Enhanced mood and mental clarity
Your gut and brain communicate via what’s called the gut-brain axis. Your gut microbiome plays a crucial role in effective crosstalk between the two. When your gut microbiome is off balance, it may affect your mental health.
More research is needed on the connection between probiotics and mental health, as results from current studies vary.
Better sleep quality
Your gut-brain axis also plays a role in how well you sleep. Probiotics may bolster communication along this internal information superhighway by signaling the production of neurotransmitters that affect mood, feelings of well-being, and more. One study randomized 70 participants to receive either a multi-strain probiotic or a placebo for six weeks. Those taking the probiotic reported improved sleep when compared with the placebo group.
Supported immune system
Probiotics may support immune health in several ways. First, as noted above, they enhance gut health, including by strengthening the intestinal barrier. The intestinal barrier helps keep toxins and germs from entering the rest of the body. Additionally, probiotics stimulate immune cell responses and antibody production to help ward off infections and harmful substances. They also promote production of anti-inflammatory cytokines to help combat inflammatory processes.
Improved skin health
Here’s a way you might be able to literally see if your probiotic is working. Just as we have a gut-brain axis, we also have a gut-skin axis, meaning our gut microbiome informs our skin health. Probiotics may help reduce inflammatory processes and may also help alleviate acne vulgaris by balancing microbiome health and inhibiting the growth of bacteria that contribute to the condition.
Improved glucose metabolism
As noted above, some probiotics may help with glucose metabolism or our ability to maintain healthy glucose levels. When the probiotics in your gut ferment prebiotics (things like fiber) from the foods you eat, the probiotics produce short-chain fatty acids (SCFAs), which signal the body to stimulate the production of glucagon-like peptide 1 (GLP-1). Probiotics can also stimulate GLP-1 production through other mechanisms.
GLP-1 is a hormone produced in the gut that helps with glucose control and can improve insulin sensitivity. Eating causes your glucose level to rise in your bloodstream—hence the term “blood sugar.” In response to this, your pancreas produces and releases insulin, a hormone that helps tell cells to utilize glucose for energy.
GLP-1:
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Helps your pancreas produce more insulin, which can then help lower blood sugar.
- Stimulates areas in the brain that help us feel full.
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Slows gastric emptying, which can slow the absorption of glucose into the bloodstream, helping to lessen the chance of experiencing high blood sugar after a meal.
People with type 2 diabetes have insulin resistance. In other words, their cells no longer respond as well to insulin, and their blood sugar levels remain high. Beta cells in the pancreas respond by producing even more insulin, but eventually, they can’t keep up with the demand, causing blood sugar to increase. Changes in insulin sensitivity can begin well before glucose levels increase to the ranges consistent with prediabetes and diabetes, however.
If you have type 2 diabetes, your body may secrete less GLP-1. But, even without diabetes, a lack of beneficial bacterial strains in the gut may also mean you’re not effectively producing GLP-1 in response to a meal—so a probiotic formulated to help increase GLP-1 can be beneficial.
Tracking whether a probiotic is helping with blood sugar control is a little more complicated than keeping a journal. With the help of your healthcare provider, you can monitor blood sugar metrics over time via blood tests:
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Fasting glucose level: Measures your blood sugar after at least eight hours of fasting.
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HbA1C: Measures your average blood sugar over the past three months.
If you wear a continuous glucose monitor (CGM), you can also track how high and for how long your blood sugar spikes after a meal. After taking a probiotic that helps produce more GLP-1, you may notice that the large peaks on your CGM readout have changed to more of a rolling-hill pattern. This would be a good sign that your probiotic is helping with your blood sugar management.
By the way, if the term GLP-1 sounds familiar, that’s likely because you’ve heard about medications that are a synthetic form of this hormone. They help treat type 2 diabetes and obesity. Probiotics can help increase your body’s natural production of it.
Balanced weight and appetite
People who are in the overweight or obese categories of body mass index (BMI) may experience reduced GLP-1 secretion. So boosting GLP-1 by taking certain probiotic strains may help you maintain a healthy weight for a few reasons.
Insulin resistance, which is linked to obesity, can lead to difficulty maintaining a healthy weight, since excess insulin drives fat storage.
You may experience cravings for foods, such as processed carbs, sweets, and more, that will ratchet up your blood sugar fast. But a rapid rise can lead to a vicious cycle of blood sugar spikes and crashes, followed by cravings and consumption of foods that can lead to weight gain.
The GLP-1 hormone also helps slow gastric emptying, which can help you feel fuller and more satisfied from your meals and snacks. And GLP-1 helps calm “food noise,” a term that many experts use to describe constant cravings and intrusive thoughts about food.
Another hormone, leptin, shares links to food noise. Your fat tissue produces leptin, which tells your brain you’re full while eating. But too much leptin can cause leptin resistance, where your brain ignores leptin’s signal. The bottom line is that once someone is in the obese or overweight BMI categories, then complex mechanisms may be at play for their body to maintain what’s called a weight “set point” and they may need additional tools, beyond lifestyle changes, to manage weight.
After promoting your body’s natural GLP-1 production by taking appropriate strains of probiotics consistently over time (along with focusing on nutrition), you may notice you feel less hungry, experience fewer cravings, and eat less food overall. These are all signs your probiotic is doing its job.
More energy
Many of the mechanisms already mentioned related to probiotics might also put some extra pep in your step. For example, if your overall mental health and mood improve, you might feel more energized.
When you feel more energetic, you may feel more motivated to engage in physical activity. And you may find that probiotics give you a perceived boost in performance and recovery.
A 2023 systematic review of 13 studies about probiotics in athletes found that “the evidence suggests that the integration of athletes’ diets with some bacterial strains and also the consumption of multi-strain compounds may lead to an improvement in performance and can positively affect performance-related aspects such as fatigue, muscle pain, body composition, and cardiorespiratory fitness.”
And a 2025 narrative review found that “the literature suggests that improved recovery after intense training regimes, enhanced nutrient absorption, alleviation of gastrointestinal symptoms, and improved immune function may underpin the beneficial effects of probiotics on sporting performance.”
Signs probiotics may not be working
“Ironically, sometimes things have to get worse before they get better,” Dr. Cutcliffe says. “And the introduction of powerful probiotics can mean immediate gastrointestinal changes that are usually fantastic, but sometimes challenging.” For example, you might at first experience gastrointestinal symptoms, such as gas or bloating, that feel counterintuitive for a short time as your body adjusts. But then your symptoms may start to improve.
How to maximize the effectiveness of probiotics
As with any supplement, probiotics are not a magic bullet to solve health issues on their own. Instead, they work as a supportive tool for overall health. Here are some lifestyle changes that might amplify results.
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Boost physical activity: As your energy increases, for example, you may wish to engage in more physical activity or revamp your existing regimen. Physical activity also supports blood sugar management.
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Prioritize sleep and manage stress: Stress and poor sleep can worsen gut and metabolic health. Aim for at least seven hours of quality sleep per night and engage in calming activities or hobbies when possible.
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Make dietary changes: To boost the results of probiotics, you may wish to reduce intake of processed carbohydrates, ultra-processed foods, and added sugar. Consider an additive approach by reaching for more whole foods. Additional dietary changes can also support your gut microbiome, which further promotes overall health. “The best dietary way to boost probiotics is by eating the prebiotics (foods) that feed them,” Dr. Cutcliffe said. “Foods high in fiber and polyphenols are great. Think about your produce section in the grocery store: leafy greens, berries, sunchokes, asparagus, etc.”
When to consult a healthcare provider
If you experience ongoing issues with any health concerns or adverse symptoms from probiotics, you should reach out to your healthcare provider.
Key takeaways
- Probiotic foods and supplements help feed your beneficial gut microbiota.
- Probiotics help improve gut health by balancing the microbiome; they also produce beneficial substances that help regulate hormones, blood sugar, and more for improved health.
- Probiotics can boost mental and physical health, help with weight management, improve metabolic health, and may even support exercise performance and recovery.
- You can tell if your probiotic is working by monitoring yourself for symptom changes or other measures of improved health.
- Remember, probiotics take time to work, and a healthy diet as well as other lifestyle changes can maximize their benefits.
FAQ
How can I tell if a probiotic is working?
You can tell if a probiotic is working by assessing whether you’ve noticed beneficial changes in your gut health (such as fewer gastrointestinal symptoms), your metabolic health (such as improved health metrics and weight management), or your mental health (such as an improved mood or a reduction in brain fog).
Why do cardiologists warn against probiotics?
Cardiologists and other healthcare providers may advise patients with compromised immune systems or severe illnesses to take supplements only under their supervision. However, early research suggests that probiotics may have a beneficial effect on cardiovascular health because gut health informs heart health. Still, people with cardiovascular concerns should consult their doctor before taking any new supplements, including probiotics.
How long after taking probiotics will I notice a difference?
Keep in mind that everyone’s experience with probiotics is a little different. You may notice a difference after taking a probiotic in as little as one day or it could take up to several months of consistent use to see real results. Likely you’ll notice changes to your gut health and digestion first, before potentially experiencing changes to your metabolic health.
What stops probiotics from working?
Improper storage can impact the effectiveness of probiotics, so always follow the storage directions on the container of your probiotic supplement. Many should be refrigerated and kept away from light and humidity. Every person will experience the effects of a probiotic a bit differently, as well. Individual factors can also impact how well a probiotic works for you, including the current makeup of your gut microbiome. For example, if you have an overabundance of certain bacteria, your probiotic strains may need to compete significantly with those microorganisms, making the supplement less effective in the short term.
Can probiotics make you sleepy?
Probiotics may improve your sleep quality over time, but they don’t directly make you feel sleepy.
