Why do i sometimes wake up with iodine taste?

Could be Acid reflux: See your primary care provider to get checked for Acid reflux disease, Indigestion or other GI problem. Also schedule a dental check up. Eat healthy, exercise and avoid tobacco and alcohol.

Reflux: That is most likely from acid reflux. You can get bile as well as acid, and it's a very bitter taste. Acid reflux can be worse at night when you are laying flat and acid is not buffered by food. It's important to know if you have that so I would check with your doctor and see if he wants to do some tests like an upper G.I. or put you on acid suppressing medicine like Prilosec.

Many causes: It appears you're not on any medications, but if you were, that is typically the most common cause. Consider unhealthy oral hygiene. Other causes include food allergy's, peptic ulcer disease, too much iron, high calcium, too much lead, kidney disease, and other metal overloads. Serious, but less likely conditions, such as cancer, can cause it so make appointment with doctor ASAP for evaluation.