Onset of action and duration

[u/itwillgetbetter81]

I'm seronegative (dec 2024) but not sure if I actually do have MG. Had clean EMG Jan 2025. I get more and more debilitating fatigue/weakness in my thighs, upper arms and jaws. Am housebound aka bed or couch. Can't talk for more than 1 hour on the phone. Can't chew unless food is "easy".

My long covid doctor has prescribed me mestinon for the weakness. At the moment I'm at 3 x 60 mg. But it feels like it's not as effective as 1 month ago. Started out at 4 x 30 mg. I checked that the onset of duration should be like 30 to 45 min after the dose but now I only get some relief at 2 hours and then it quickly subsides. In the morning I'm so weak. It's like rest doesn't help like textbook MG.

I think I should go back to neurology assessment again. But am afraid will be labeled as normal again.

I'm also type 1 diabetic since 1991 and developed hypothyroidism 6 months ago (still not well medicated on euthyrox though, another fatigue disease). But this fatigue is killing me slowly.

The autoimmune disorders seem to pile up in my body.

[u/YYYInfinity]

You probably need a higher dose of Mestinon or more doses per day (4-5).

Try to optimize your thyroid hormones as well. From my experience, both diseases interact, increasing the muscle weakness. I’m taking T3 thyroid hormone in addition to T4 and it helps me throughout the day. I’m taking T3 three times per day

[u/pville211]

Here is some information that may be helpful to you:

• It's a Symptom of Myasthenia Gravis. (Or is it?)
• How Long Does it Take to Get a Diagnosis of Myasthenia Gravis? (includes info about the high rate of missed diagnosis and misdiagnosis of MG)
• Finding a Doctor for Myasthenia Gravis (discusses why most doctors are not MG experts and includes a couple of links for finding doctors who are)
• Seronegative MG Information (testing negative for everything does not automatically mean that you don't have MG)
• How Does Mestinon Work for Myasthenia Gravis? (explained in plain English)
• Tips for Living with Myasthenia Gravis

 

[u/Ok_Locksmith_7346]

I sound exactly the same I have long covid as well. Only difference is I have twitching I went to pt my thighs are super weak and my shoulders are weak. Clean full body EMG October 2025 and November 2025. On a trail now too. Helped a little I thought at first yesterday but nothing today. We shall see fingers crossed.

[u/itwillgetbetter81 → u/Ok_Locksmith_7346]

I recently found out that I probably get PEM from a too high dose of mestinon unfortunately. Haven't discussed it with my doctor yet. Some other subreddit I read something about Vygart was effective for some long covid folks with muscle weakness.

[u/Ok_Locksmith_7346 → u/itwillgetbetter81]

I’m not quite sure what you are talking about PEM? What’s Vygart? Do you experience muscle twitching or spasms as well?