
Your body makes chains of amino acids to create new proteins, and creatine is one such amino acid. You can produce your own supply of creatine, and the nutrient is also present in meats. In some cases, your doctor may prescribe creatine supplements to help with a medical condition or to treat a deficiency. Do not supplement without medical supervision, and follow your doctor's instructions to avoid potential health problems.
Overdosing

Follow your doctor's prescription regarding dosage and frequency when taking creatine. According to MedlinePlus, it is possible that high doses of the amino acid cause kidney, heart and liver damage, although this is still under study.
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Exceeding Treatment Duration

Creatine supplements are available without a doctor's prescription, but do not take them longer than your physician recommends. Six months is usually the maximum durantion to prevent side effects, which include muscle discomfort, diarrhea, weight gain, hypertension, liver and kidney problems as well as dizziness.
Low Water Intake

Most of the creatine you take finds its way to your muscles. From there, it pulls water from the other parts of your body into the muscle fiber. Drink at least 64 ounces of water daily to make up for the fluid loss and prevent dehydration.
Becoming Overheated

While you are on creatine supplements, avoid working out in hot conditions. Go to an air-conditioned gym or work out outside very early in the morning or past sundown. Because creatine takes fluid from other areas of your body and deposits it in your muscles, you can become dehydrated quickly if you exercise in the heat.
Pregnancy and Breastfeeding

The science is incomplete on the effects of creatine on fetuses and infants. However, MedlinePlus recommends avoiding pregnancy and breastfeeding for the duration of your treatment to be on the safe side.
Obscure Brand Names

The University of Maryland Medical Center cites reports of contaminated creatine supplements. The clinic recommends that you buy products from well-known companies to minimize the risk of getting a tainted item. Ask your doctor for a recommendation on brand or vendor.
NSAIDs
Non-steroidal anti-inflammatory drugs -- NSAIDs -- are a class of pain relievers that also reduce fever and inflammation; ibuprofen is one such medicine. When you take creatine and a NSAID, you increase the potential for kidney damage. Ask your doctor in advance which painkiller is safe in case you need it.
Caffeine and Ephedra
MedlinePlus reports the case of an athlete who had a stroke after taking creatine, caffeine and ephedra for six weeks. Other supplements were also part of the patient's regimen, making the evidence against the three-substance blend less than firm. Nevertheless, be cautious and get a doctor's advice before taking the same combination.
Diuretics

Diuretics are drugs formulated to remove excess water from your bloodstream to ease the pressure against the walls of your veins. Creatine also redirects fluids into the muscles. Thus, when you take diuretics and creatine concurrently, you increase the potential for dehydration and kidney damage.
Other Drugs
Two other drugs -- cimetidine for ulcers and probenecid for gout -- combined with creatine raise the risk for kidney damage. Disclose to your doctor all prescription and over-the-counter items you take to avoid harmful interactions.