Fatigue is best described as a lack of energy, tiredness or weariness, according to MedlinePlus. Fatigue can result from taking certain medications or from underlying medical conditions. Stopping or adjusting your medications or treating the condition causing this symptom can help to alleviate it, but sometimes this is not enough. Vitamins can also help you gain energy and alleviate tiredness. Before trying any vitamins to fight fatigue, however, consult your doctor.

Vitamin B12

This vitamin, also known as cobalamin, helps to create energy by converting carbohydrates into glucose. When you have low vitamin B12 levels, you may experience shortness of breath, tingling in the toes and fingers, fatigue, diarrhea, numbness or nervousness, according to the University of Maryland Medical Center. You can take B12 in supplement form or as an injection, or find it in foods such as fish, dairy products and eggs. Certain medications, however, may decrease vitamin B12 levels in the body and may not be taken with a B12 supplement, including tetracycline antibiotics, anticonvulsants, colchicine, H2 blockers, proton pump inhibitors, chemotherapy medications, bile acid sequestrants and metformin, according to UMMC.

Vitamin D

Vitamin D plays several critical roles in the body, such as aiding in the metabolism and absorption of phosphorus and calcium and regulating more than 200 genes, according to Women to Women. If you are deficient in vitamin D, you may experience fatigue, muscle pain, bone fracture and weakness, low energy, depression symptoms, sleeping troubles, mood swings and reduced immunity. You can get vitamin D in a supplement, or through sunlight exposure and certain foods, such as egg yolks, salmon and cheese. Taking too much vitamin D may cause nausea and vomiting, serious heart problems and confusion, according to the National Institutes of Health Office of Dietary Supplements. Some medications may interfere with vitamin D, such as cholesterol-lowering medications, weight-loss medications and anti-seizure medications.

Vitamin B5

Also referred to as pantothenic acid, vitamin B5 may be beneficial to improving fatigue and several medical conditions that may cause it, such as chronic fatigue syndrome, multiple sclerosis, stress and depression, according to MedlinePlus. In addition to taking supplements, you can obtain this vitamin by eating certain foods, such as mushrooms, sunflower seeds, strawberries, broccoli and cauliflower. Taking too much vitamin B5 may cause diarrhea, heartburn and nausea, however. Speak to your doctor before taking vitamin B5 in conjunction with gingko biloba, saw palmetto or garlic, or medications used to treat dementia and Alzheimer's disease or muscle weakness disorders like myasthenia gravis.