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If the above-mentioned symptoms linger for more than a few weeks or get worse, then call your doctor or head to a walk-in clinic. While in a clinic or hospital, your doctor can confirm a diagnosis of giardiasis by taking a stool sample and looking under a microscope for parasitic spores. A stool antigen test and trichrome staining techniques are also available to diagnose Giardia.  As a rule, it takes 3 different stool samples to diagnose 90% of Giardia cases. Lab technicians look for a high concentration of either spores or trophozoites. Staining might not be sufficient to identify Giardia because variable concentration levels can make people sick — some people are more sensitive to the parasite than others. If your diarrhea is severe and you're unable to replenish your fluids at home, you may need to get treated at a clinic or hospital for dehydration. As such, if dehydration symptoms appear (see above), call your doctor and ask for advice on where to go. The best way to replace water and electrolytes (such as sodium, potassium and calcium) is intravenously, which requires a needle to be inserted into a vein in your arm.  While you're on intravenous, you can also be given glucose and various essential vitamins, which can give you more energy and reduce your mental fog. An intravenous session typically lasts a few hours, although you may need to stay overnight(s) if your dehydration and/or malnourishment is severe. You may be given some oral rehydration solution to take home — they typically contain electrolytes and glucose dissolved in water. Some antibiotics are effective for also killing parasites, so ask your doctor about getting prescribed one if your giardiasis lasts for much more than 2 weeks. Commonly prescribed antibiotics for giardiasis include metronidazole, tinidazole and nitazoxanide. Furazolidone and quinacrine are also effective for treating giardiasis, but no longer available in the U.S.  The most common antibiotic used to combat giardiasis is metronidazole (Flagyl) — it has an efficacy rate of between 75-100%, but it often causes nausea and a metallic taste as side effects.  Tinidazole (Tindamax) may work even better than metronidazole for giardiasis and it can be given in a single dose, but it also causes some side effects. Nitazoxanide (Alinia) comes as a liquid and may be easier for children to swallow and tolerate. Paromomycin and albendazole are less effective medications for giardiasis, but still sometimes used. If your diarrhea persists for more than a few weeks, it's tempting to put a stop to it with medication, but your doctor may advise against it. Sometimes anti-diarrheal medicines can prolong the infection and make your condition worse because your body is prevented from getting rid of the parasite that's causing the diarrhea. Talk to your doctor about the pros and cons.  Over-the-counter anti-diarrheal medicines include loperamide (Imodium) and bismuth subsalicylate (Kaopectate, Pepto-Bismol). Bismuth subsalicylate can also be used to treat nausea and vomiting. A stronger prescription anti-diarrheal is called Lomotil, although it must be taken as soon as you start experiencing diarrhea.
Confirm a diagnosis. Get treated for dehydration. Ask your doctor about antibiotics. Use anti-diarrheal medication cautiously.