Creatine is one of the most popular gym supplements in the world, but new headlines about worrying side effects have left many people wondering if it’s actually safe or if they personally should avoid it. In this guide, we unpack what the research really says, who may need to be cautious, and how to use creatine more safely if you choose to take it.


If you’ve spent any time in a gym, you’ve probably seen a tub of creatine on the counter or in someone’s shaker. It’s marketed as a simple way to lift heavier, build more muscle, and recover faster. At the same time, articles and social media posts keep warning that “certain people should avoid creatine” because of potential side effects, especially around the kidneys and water retention.


The truth is more nuanced: for many healthy adults, creatine is well-studied and generally safe when used correctly. But there are specific groups of people who should think twice or only use it under medical supervision. Let’s walk through this clearly so you can make an informed, confident choice.


Creatine is one of the most widely used sports supplements, but it isn’t right for everyone.

What Is Creatine and Why Are People Worried About It?

Creatine is a compound your body naturally makes from amino acids and stores mainly in your muscles. It helps rapidly regenerate ATP, the main energy currency your muscles use for short, intense efforts—think heavy squats, sprints, or explosive lifts.


Creatine monohydrate (the most studied form) has been shown in many trials to:

  • Increase strength and power output in resistance training
  • Support small but meaningful gains in lean muscle mass over time
  • Improve performance in repeated high-intensity efforts (e.g., sprint intervals)

So why the concern? Recent media stories—including those highlighting “worrying side effects” and warnings for specific people—tend to focus on:

  1. Potential stress on the kidneys
  2. Water retention, bloating, or sudden weight gain
  3. Digestive upset when dosing is aggressive or quality is poor
  4. Confusion about lab tests (especially creatinine levels)

“In healthy adults, creatine monohydrate is one of the most extensively researched sports supplements and appears safe when used at recommended doses. The real caution is for people with pre-existing kidney disease or those taking certain medications.”

– Summary of findings from peer‑reviewed reviews (e.g., International Society of Sports Nutrition position stands)

Who Should Be Cautious or Avoid Creatine Altogether?

Most of the alarm around creatine comes down to a key point: not everyone is starting from the same baseline of health. The people most likely to run into real problems are those who already have medical vulnerabilities—especially involving the kidneys, heart, or fluid balance.


1. People With Kidney Disease or Reduced Kidney Function

This is the biggest, most consistent red flag. Creatine is broken down into creatinine, which your kidneys filter out. In someone whose kidneys are already struggling, extra creatine can potentially add stress or muddy the picture when doctors interpret lab tests.

  • Chronic kidney disease (CKD)
  • History of glomerulonephritis, polycystic kidney disease, or other structural kidney issues
  • Single kidney (including after donation) unless a nephrologist explicitly approves creatine use
  • Unexplained elevated creatinine levels on prior blood work


2. People Taking Kidney-Stressing Medications

Some drugs can be hard on the kidneys or affect fluid and electrolyte balance. Adding creatine on top may not be wise without close monitoring.

Examples to discuss with your doctor include:

  • NSAIDs used regularly (e.g., ibuprofen, naproxen) at high or chronic doses
  • Certain blood pressure medications (ACE inhibitors, ARBs, diuretics)
  • Some chemotherapy agents and antiviral medications
  • Drugs that alter creatinine or interact with high-protein diets

3. People With Serious Heart or Fluid-Balance Conditions

Creatine causes your muscles to hold more water inside their cells. For the average healthy lifter, that’s usually a mild, manageable side effect. But if you have a condition where fluid retention is dangerous, even seemingly small shifts can matter.

  • Congestive heart failure
  • Severe hypertension that isn’t well controlled
  • Advanced liver disease with fluid buildup
  • Certain rare metabolic or neuromuscular disorders

4. Adolescents and Pregnant or Breastfeeding People

Research on creatine in healthy adults is robust. In teenagers and pregnant or breastfeeding people, the data is far more limited.

  • Teens: Some sports medicine groups are cautious about routine creatine use in minors unless supervised by a qualified sports physician or dietitian.
  • Pregnancy & breastfeeding: Because high‑quality safety studies are lacking, most clinicians recommend avoiding supplemental creatine unless there’s a very specific medical indication and specialist oversight.

5. Anyone With Unexplained Swelling, High Blood Pressure, or Lab Changes

If you’ve started creatine and notice:

  • Sudden, persistent ankle or leg swelling
  • Headaches and rising blood pressure
  • Shortness of breath or chest discomfort
  • Lab tests showing rapidly rising creatinine or abnormal kidney markers

stop the supplement and talk to your clinician promptly. In these cases, you may be in the group of people who should avoid creatine entirely.


The Most Common Creatine Side Effects (and What They Actually Mean)

Not all side effects are dangerous, but they can still be uncomfortable or inconvenient. Understanding what’s normal—and what’s not—can help you decide whether creatine is worth it for you.


1. Water Retention and Scale Weight Jump

Many people gain 1–3 kg (2–7 lb) of body weight in the first couple of weeks on creatine. This is mostly water drawn into muscle cells, not fat.

  • Muscles may look “fuller” or more pumped.
  • Some people feel puffy, especially if sodium intake is high.
  • This effect is often more dramatic with high “loading” doses.

2. Bloating or Digestive Upset

Stomach discomfort, loose stools, or cramping are usually related to:

  • Very high single doses (e.g., 10–20 g at once)
  • Poorly dissolved powder or low-quality products
  • Taking it on an empty stomach when you’re sensitive

3. Elevated Creatinine on Blood Tests

Creatinine (with an “n”) is a breakdown product that doctors use as a proxy for kidney function. When you take creatine, your creatinine can rise slightly—even if your kidneys are healthy.

This is one reason some clinicians are cautious: they have to interpret whether a higher number is due to:

  • Actual kidney damage (which is serious), or
  • Supplement‑related changes plus higher muscle mass

“An isolated bump in creatinine in a muscular person using creatine doesn’t automatically equal kidney failure—but it does mean we need to look at the whole picture: other kidney markers, urine tests, blood pressure, and symptoms.”

– Perspective commonly noted in nephrology and sports medicine practice

Who Generally Tolerates Creatine Well?

For context, it’s helpful to know that in healthy adults, creatine is one of the most researched sports supplements available. When used at recommended doses, multiple large reviews have not found convincing evidence of kidney damage in people without pre‑existing kidney disease.


People who are more likely to tolerate creatine well (with appropriate dosing and hydration) tend to be:

  • Healthy adults with normal kidney and heart function
  • People doing regular resistance training or high‑intensity sports
  • Those who eat little red meat or fish and may have slightly lower baseline creatine stores
  • Older adults using creatine alongside strength training under professional guidance

Person lifting weights in a gym setting
In healthy adults who train regularly, creatine can modestly support strength and performance when used correctly.


How to Use Creatine More Safely (If You Choose to Take It)

If you and your healthcare provider decide creatine is appropriate, a few practical habits can reduce the chance of uncomfortable side effects.


1. Skip the Aggressive Loading Phase

Traditional advice suggests taking 20 g per day (in 4 doses) for 5–7 days, then dropping to 3–5 g per day. While this works, it also increases the risk of bloating and digestive issues.

A gentler, often better‑tolerated approach:

  • Take 3–5 g once daily from the start.
  • Expect benefits to show up more gradually over 3–4 weeks.

2. Use Creatine Monohydrate From a Reputable Brand

Most of the safety and performance research is on creatine monohydrate, not fancy “new” forms. Look for:

  • Third‑party testing (e.g., Informed-Sport, NSF Certified for Sport)
  • Simple ingredient list (just creatine monohydrate, ideally)
  • Clear dosing instructions and batch numbers

3. Take It With Food and Plenty of Water

To reduce stomach upset:

  • Mix creatine into a well‑hydrated drink (such as water plus a bit of juice or a post‑workout shake).
  • Take it with a meal or snack rather than on an empty stomach.
  • Aim for at least 1.5–2.5 liters of fluid per day, adjusted for your size, climate, and activity.

4. Monitor Your Body and Your Labs

Before starting, and again after a few months, it’s reasonable to:

  • Check kidney function (creatinine, eGFR, and sometimes cystatin C)
  • Track blood pressure, weight, and how your body feels
  • Note any swelling, unusual fatigue, or changes in urination

If lab markers worsen or symptoms appear, stop creatine and review everything with your clinician. It’s better to be cautious than to chase marginal performance gains at the expense of your health.


Person consulting with a healthcare professional, reviewing health information on a tablet
Discuss creatine with a healthcare professional who understands your medical history, especially if you have kidney, heart, or blood pressure concerns.

A Realistic “Before and After” of Using Creatine

It’s easy to see dramatic “before and after” transformation photos online and assume creatine is a magic powder. In reality, its effects are incremental and depend heavily on your training, sleep, and nutrition.


Person resting at the gym before starting a structured supplement and training plan
Before: Training hard but inconsistent with sleep, nutrition, and hydration. Creatine alone would offer limited benefit here.
Person performing a barbell squat as part of a structured strength program
After: With a solid strength program, better recovery, and appropriate creatine use, small but compounding performance gains are more realistic.

In practice, many lifters notice:

  • Slight increases in reps or load over months, not overnight transformations
  • Subtle changes in muscle fullness and bodyweight
  • Performance dips if they stop creatine after long‑term use, which then stabilize


Common Obstacles and How to Overcome Them

Even when creatine is medically appropriate, it can create practical hurdles. Here’s how to navigate the most common ones.


“The Scale Jump Freaked Me Out”

For many people—especially those with a history of dieting or body image struggles—a sudden jump in scale weight can feel alarming.

  • Remember that early increases are usually water in muscle, not fat gain.
  • Focus on performance markers (strength, endurance) rather than just the scale.
  • If weight changes are distressing, creatine may not be psychologically worth it right now—and that’s okay.

“My Doctor Said My Creatinine Is High”

If you’re on creatine and your blood tests show higher creatinine:

  1. Tell your clinician you’re taking creatine and roughly how long you’ve used it.
  2. Ask whether they looked at other markers (eGFR, cystatin C, urine tests, blood pressure).
  3. Be open to stopping creatine temporarily and retesting to clarify what’s going on.

“I’m Not Sure If It’s Helping”

Creatine’s effects can be subtle. To get a clearer sense:

  • Keep a simple training log for 8–12 weeks (sets, reps, weights).
  • Note changes in performance, recovery, and how you feel during hard sets.
  • Compare your progress with and without creatine over similar training blocks.

What the Science Says (In Plain Language)

Dozens of trials and multiple position stands from sports nutrition organizations converge on a few key points:

  • Creatine monohydrate is effective for improving strength and high‑intensity performance in many healthy adults.
  • At typical doses (3–5 g per day), it has not been shown to damage kidneys in people without pre‑existing kidney disease.
  • There is less evidence in certain populations (kids, pregnancy, serious chronic disease), so caution is advised.

For deeper reading, you can explore:


Putting It All Together: Should You Take Creatine?

The most important takeaway is that creatine is not inherently “good” or “bad”—it’s a tool. For some people, it’s a well‑researched, relatively low‑risk way to nudge performance and muscle gains forward. For others, especially those with kidney, heart, or fluid‑balance issues, the potential downsides outweigh the benefits.


A simple decision framework:

  1. Check your health status. If you have kidney, heart, liver, or significant blood pressure issues, or take medications that affect the kidneys, talk to your doctor first.
  2. Clarify your goals. Are you chasing marginal gym gains, or do you have clinical reasons (e.g., age‑related muscle loss) to consider creatine?
  3. Decide if side effects are acceptable. If small weight changes or mild bloating would be distressing, it may not be worth it.
  4. Re‑evaluate regularly. Supplements should evolve with your health, training, and life stage—not be “set and forget.”

You don’t need creatine to be strong, healthy, or “serious” about training. If you do choose to use it, do so intentionally: start with the lowest effective dose, choose a reputable product, stay hydrated, monitor your health, and keep your medical team in the loop.


Your next step: Before you buy another tub, take five minutes to list your medications, health conditions, and training goals, then bring that list to your next appointment or telehealth visit. A 10‑minute conversation could be the difference between safe, effective supplementation and unnecessary risk.