The recommended dose is to bowel tolerance. That is so the stool is soft, but not runny. A hypothyroid condition can contribute to weight gain and to weakness. Kelp tablets also help. Natural thyroid supplements often aren't equally active from one batch to another, so this is one case where an artificial thyroid supplement may give better results.
Acupuncture can often help.
Degenerative myelopathy also can cause weakness. For further information, see the degenerative myelopathy FAQ . I have a dog in otherwise good health who has just been diagnosed with demyelinating disease of the spinal cord and nerves with loss of position sense in his back feet with progressive paralysis. This sounds like degenerative myelopathy. Aminocaproic acid n-acetylcysteine acupuncture 9.