Apparently, clen has a half-life in the body of 48 hours making it pretty much irrelevant when you take it. This means that two days on, two days off, conserves the number of pills you use in a cycle rather than for receptor downgrade which occurs around two weeks. Cytomel fights the deiodinase impairment. On a clen cycle, a potassium supplement helps maintain your electrolyte status and reduces problems with muscle cramping. Nervousness, tremors of the hands, headaches, early onset asthma and insomnia.
Muscle cramps are the most common.
If you have a job that requires lots of manual dexterity then clen can be more problematic. The tremor it gives in the hands can make steady fine movements virtually impossible. Fortunately, this effect often diminishes over a week or two of continued usage. Buy a good blood pressure monitor and use it several times a day. Base your dosage on your BP and resting pulse and your lack of side effects.