Melatonin, Sleep, and Type 2 Diabetes

My constant search for a better understanding of the Type 2 diabetes that entered my life fifteen years ago keeps bringing me back to problems with sleep. It raises the question: Why is there such a strong link between poor sleep and Type 2?

Part of the sleep connection may lie in melatonin. As it turns out, melatonin has a lot in common with insulin. Both are hormones, though melatonin is produced by your pineal gland in the brain, while insulin is made in your pancreas (and also to some degree in the brain). Problems with either hormone are associated with diabetes.


Test show that melatonin is often low in people with the metabolic syndrome, which is a risk factor for Type 2 diabetes. The latest research has deepened evidence of a relationship between melatonin and regulation of insulin production in the pancreas.

Researchers began investigating when studies showed that nurses who worked the night shift had a higher incidence of metabolic syndrome and Type 2 diabetes. Other shift workers were also found to have the same problem.

The researchers found that messing up the circadian rhythm, which makes us want to sleep in the dark and be awake during the day, lowers our levels of melatonin and serotonin. By studying rats, they found that this rhythm is tied up with insulin production, too.

In young people without diabetes, melatonin levels are higher at night while insulin levels are low, and during the day melatonin is lower while insulin is higher. It is all part of our natural circadian rhythm.

But as we age, the melatonin levels lower. One result is that older people do not sleep as well.

What this sounds like to me is that melatonin affects sleep, which affects insulin, which in turn affects melatonin. It is a cycle I would love to know how to break.

Why should you care?
What if there are things we can do about this? The first thing I wondered was why not take a melatonin supplement? Melatonin is given to people who suffer from jet lag or who have severe insomnia. Why not people with diabetes as well?

Someone else already had that idea. What they found was that for people with Type 2 diabetes the supplement caused blood sugar to rise and be harder to control. Besides, the long-term effects of melatonin supplements are not fully known.

What can you do?
Happily, you can increase your melatonin in other ways. First, expose yourself to sunlight early in the morning, at least fifteen minutes of it. This boosts serotonin, the daytime hormone that turns into melatonin at night.

Get your circadian rhythm started early in the morning with bright light, and you will get more melatonin at night. And while you are getting sunshine, do a little exercise too. Serotonin will get a boost, and so will your mood.

To encourage melatonin release at night, lower the lighting for a while before bedtime, and sleep in complete darkness. This will also improve your sleep, which will improve blood sugar control as well.

You also need to understand where the melatonin in your body comes from. As I noted above, it is a product of serotonin metabolism, and serotonin comes from tryptophan.

Where do you get tryptophan? The best source of this powerful substance is food. If you eat things high in tryptophan, you will improve your chances of producing enough melatonin.

Have you heard that Thanksgiving dinner makes you sleepy because of the tryptophan in turkey? Well, that is not entirely true. Chicken has the same amount of tryptophan, and there is more in seafood and red meat.

The foods that are highest in tryptophan are spirulina (seaweed), dried egg whites, and soy products. There is also a lot of tryptophan in watercress, which is a fresh salad green, and in spinach, too. Cheeses, walnuts, and roasted pumpkin seeds are also among the foods that have large amounts of tryptophan.

So it will not be hard to get plenty of tryptophan without using supplements — it is always better to get the things you need from your food if possible. However, l-tryptophan is available everywhere vitamins are sold.

Be aware that the supplement passes the blood–brain barrier at a higher rate than the tryptophan in foods. It is sometimes used by people who have depression and sleep disorders, among other things.

This is some of what I have learned about melatonin’s link to Type 2 diabetes. I hope it helps you and that you are not overwhelmed by yet another side of this difficult journey.

Take care of yourself. You matter.

  • olpind

    Just curious about the source of data for the statement “that for people with Type 2 diabetes the supplement caused blood sugar to rise and be harder to control.” According to this is not the case. Those who took a melatonin supplement before bed actually lowered their A1C.

    • Diane Fennell

      Hi olpind,

      Thanks for your question and for your careful reading of the piece! According to the National Institutes of Health, “Melatonin might increase blood sugar in people with diabetes. Monitor
      your blood sugar carefully, if you have diabetes and take melatonin.” (

      Diane Fennell
      Web Editor

      • olpind

        Thank you.

  • John york

    I am 87 yeasts old, still working,am 6’2″ tall and weigh 230 lbs. I have, since birth been a heavy milk drinker and still am. For many years milk and milk products straight from the cow. For years now 2 percent milk. I have been diagnosed as a type 2 diabetic, take metformin twice a day. Very seldom check my own blood sugar. And each time my doctor checks me his comment is “your diabetis is under fantastic control”. I eat some sweets , love sweets, and there is nothing better than a tall glass of. Cold milk. Go figure. John York

  • Erik Rokisky

    Why did the blood glucose rise when given melatonin..? Curious!