Also iron, and B-vitamins should also be considered anytime fatigue and autoimmune diseases are an issue.
You can get tested, but if you don't want to wait, you can try some of these one at a time and see how you feel. Try some B6, tryptophan and iron together for a boost in serotonin.
Vitamin A and selenium together can be a powerful energy boost, as both help convert thyroid hormones into their active version.
B12 is another big one for fatigue. Try 1000mcg today and see if you feel a difference. If you get a headache about four hours later, it's a sign of deficiency - so just take more. You can't overdose on B12. I've spent like 20 hours researching this.
Iron and vitamin A together are pretty powerful for fatigue.
Your response to all of the above suggestions will completely depend on your current nutritional status with each nutrient. Maybe vitamin A won't do much but vitamin D will. Maybe iron won't do much but a b-complex will. Trial and error is sometimes the best way to figure out what you need.
Long term, it's really important to get some of all the vitamins each day. And not to take just one or two vitamins on their own, because they all work together. Taking one vitamin may increase the requirement for another vitamin. B6 may increase requirements for B2, B3 and iron, for example.
Zinc can lower cortisol levels, which is good, but can make you sleepy. Something just to be aware of. If you try 15mg of zinc in the morning and feel tired, you probably are deficient in zinc. And for the short term you'll want to take it at night just to avoid that daytime drop in cortisol.
Limit tea, alcohol, sugar, coffee (even decaf), and raw foods as these all have anti-nutrients and will suck away your vitamins.