Depends. On who you ask. Most lab reports show normal as being 0.5 - 5 mlu/l, but many people feel the range should be 0.3 - 3. If you are being treated for hypothyroidism, the ideal range is 1 -2. I usually start to take notice when someone's TSH is >2.5. See http://www. Nlm. Nih. Gov/medlineplus/ency/article/003684.Htm.