Just commenting on hypothyroidism (which I have had for many years).

Generic levothyroxine is pushed for treating hypothyroidism because it is cheaper. But I choose a brand name even though it is more expensive and doctors and insurance push back. I have tried generic levothryoxine and I did poorly on it.

Levothyroxine (and lithium) is a Narrow Therapeutic Index (NTI) drug that is "defined as those drugs where small differences in dose or blood concentration may lead to dose and blood concentration dependent, serious therapeutic failures or adverse drug reactions" (Narrow Therapeutic Index Drugs - DrugBank).

The problem with generic levothyroxine is that the manufacturer can change with each refill, so that the dose is not consistent (Should You Take Generic Levothyroxine?). An excerpt: "A key concern about generic levothyroxine, and a valid complaint by doctors, is that every time you get a refill, you can potentially get levothyroxine made by a different generic manufacturer. Here's why this can be a problem.

"Levothyroxine is required by law to fall within 5% of its stated potency and the U.S. Food and Drug Administration (FDA) requires that this potency falls within 95% to 105%. Each company's formula for a particular dosage of levothyroxine tends to be consistent, so if drugmaker A's product is usually 96%, it will typically consistently run at about 96% potency. Similarly, if drugmaker B's levothyroxine at a particular dosage typically runs at 105% of potency, that will usually be consistent.

"So, using the example of a 100 mcg levothyroxine tablet, drugmaker A's 100 mcg tablet delivers 96 mcg of active levothyroxine. Drugmaker B's delivers 105 mcg of active levothyroxine. Going from drugmaker A to B's product would be a difference of around 65 mcg per week, which is almost like taking an extra pill each week. Conversely, if you go from B to A, it's like eliminating more than half a pill each week.

"Because pharmacies are free to fill generic prescriptions with products from any manufacturer, unlike prescriptions that specify a particular brand name, with every refill of generic levothyroxine, you run the risk of getting a product from a different drug maker that uses a different potency. This could affect your thyroid replacement stability, your hypothyroid symptoms, and your thyroid-stimulating hormone (TSH) levels."

The importance of sticking with one levothryoxine brand for treating hypothyroidism is also pointed out in a Harvard Health Publishing article (The lowdown on thyroid slowdown - Harvard Health ). "Although all brands contain the same synthetic T4, their inactive ingredients can vary, possibly affecting absorption, so it's best to stick with one brand. Also, if you're prescribed a particular brand and the pharmacy switches to a generic version, let your physician know."

The problem is that your physician may not know about levothyroxine differences among generic manufacturers that can change with each refill and not test your TSH levels with changes in manufacturers. I have had several that didn't know until I told them. Even after I told them and gave them material, they didn't seem to believe it. The push for generics is very strong and especially with Narrow Therapeutic Index drugs this can especially be a problem. The result can be that your hypothyroidism is not treated adequately, and your TSH levels bounce around.

The Harvard Health article gives info about hypothyroid symptoms, including "Mental effects. Hypothyroidism and depression share many of the same symptoms, including difficulty in concentrating, memory problems, and loss of interest in things that are normally important to you. They call for different treatments, so proper diagnosis is important."

Like others have responded to this thread, getting a good medical workup helps. It also helps to be an informed patient.

Sorry if this was too long...

Best wishes!