The difficulty with Hashi's is that there are frequent up and downs, so it can be really difficult to get to a "steady state". Honestly, I wouldn't go more than about 3 months without testing, just to make sure; though you can monitor your symptoms and decide if you need to go more or less frequently.

Because it's autoimmune you might find that calming your immune system down helps to keep your levels more stable (by reducing your antibodies). Exercise is great for that so keep up the running! If you're open to it I'd also suggest accupuncture. Many people find that a gluten-free diet helps to reduce the antibodies as well.

What meds are you on? If you're taking a synthetic T4-only supplement like synthroid or levothyroxine, you might want to look at switching to a natural/dessicated med that contains both T3 and T4 (like Armour or Nature Thyroid). This form of T4 is a lot easier for your body to process, since it's bio-identical to your natural hormones.

What labs is your doctor running? Are they basing your dose on just TSH, or are they basing it on your free T3 and free T4 test results?

I'm on Levothyroxine. I keep hearing that the natural replacements work better. I plan on asking my endo at my next apt more about it; not sure if she will order it or not. Initially, the endo did cortisol levels, TSH, T3 and T4. Now she usually does TSH along and adjusts the Levo based on the results and my symptoms that I'm having. She thinks that I'm probably someone who doesn't feel good unless my TSH is around 1.0; which has generally been true. I just wish that the level and my symptoms would stay more stable. She did suggest a low carb diet and that's helped over time.
I will definitely keep the acupuncture in mind--something that I hadn't considered at all.
Thank you!

TSH is a pituitary hormone, not a thyroid one, and is also often suppressed in people taking meds.

Do you know if she tested free or total T3 and T4? If you aren't sure, I would go ask for a free T3 test. Many people find that no matter what dose they are on they still feel awful, and it's usually because their free T3 isn't high enough.

Anyone have any insight on whether I should seek an endo or stick with my GP? I'm newly diagnosed (3 weeks ago) and just started 50 mcg of levo. I have an extensive family history on both parents' side with hypothyroid and not sure what others experience has been. I like and trust my GP, but want to feel better!

I am lucky in that I have a great GP and if needs be private health care. I tolerate levo well too but find after many years of monitoring that I need at least 25mcg more in the winter than the summer. It took almost 4 years to find a stability dose. Illness and food make a difference too. Recent diagnosis of b12 deficiency played havoc also. My levo has settled at 125 mcg (less in summer) with b12 patches and supplements.
I am a controlled type 2 diabetic.
You can monitor your levo on the site by adding a user defined field 'supplements' or 'meds' and you can use the notes section in either exercise or food to monitor tiredness and well being. Because I have a fit bit ultra I do that on the fit bit site as I check the effects on sleep too, I give myself a 1-10 rating for tiredness every day. A 6 is good and an 8 excellent, I seek to stay in that range and check, check check. Changing only one factor at a time so I know what helps, hinders or has no effect.
Biggest improvements in health:
Levo min 100
B12 patches every week (tablets tried patches better result)
1 hr exercise of any exercise daily
Adding weekly sauna for 2 hrs (relaxation or sauna itself?)
Sleep min 7 hrs( more than 8 and less than 7 harmful)
Water min 7 glasses per day
Losing bread and aspartamine from diet
Replacing oil and margarine with coconut ( thanks Debbielee)
No coffee after 4 pm
Always some breakfast

Had no effect on health
Cutting out red 2 glasses wine ( no spirits anyway) so still have a couple glasses
Changing type of exercise (stopping running so much as didn't help) cycling is fine
Eating big breakfast rather than small so now I eat what I like in a morning
Heavy protein intake so I eat protein as I feel like it
Low fat intake so I eat butter sometimes
Natural thyroid hormone costly so it doesn't help I don't spend

Detrimental on health
Exercising over 2 hrs per day intensively as overall on those days my total activity drops
Trying shredding just made me very tired
Fasting played havoc
Detoxing felt really dreadful
Cutting carbs (complex) made me very tired but cutting glucose and high fructose helped

Think the key is to monitor as much as can be monitored. Recent steroid prescription has affected my body comp but not my weight as I monitored everything on fit bit I was able to manage my health better. For me this journey is about my health not just my weight!
Although the two often go hand in hand. Ironically that which gave greatest weight loss seemed to have adverse health consequences.

Let us know how it goes

Jasmin