I feel tired since going vegan

The usual causes, what to change, and when to get a blood test.

• Last checked: Oct 2026

Feeling tired in the first weeks or months after a big change in what you eat is common, and it has a few usual suspects. Most of them are easy to fix.

Are you eating enough?

When your meals change, it is easy to end up eating less than before without noticing. If you have lost weight without trying, or you are hungry again soon after meals, eat more: bigger portions, and more legumes, nuts, seeds and whole grains.

Iron

Iron carries oxygen around your body. When you are low on it, you can feel tired and may develop iron-deficiency anaemia. A well-planned vegan diet can give you all the iron you need — the trick is helping your body absorb it:

• Eat iron-rich foods every day: beans, lentils and other pulses, leafy greens, wholemeal bread, fortified cereals, nuts and dried fruit.
• Add vitamin C to the same meal: peppers, broccoli, strawberries or oranges help your body take up iron.
• Keep tea and coffee away from meals. They reduce how much iron you absorb — leave about an hour either side.

Don’t start iron tablets on your own. If you think you might be low, ask for a blood test first.

Vitamin B12

Tiredness is one of the signs of running low on B12, and B12 is the one thing a vegan diet can’t cover without fortified foods or a supplement. If you haven’t sorted it yet, start with the B12 page.

It might not be the food

Most tiredness has nothing to do with diet. Common causes include not getting enough sleep, stress, low mood or depression, hormonal changes, illnesses and some medicines. A new diet is easy to blame — make sure it really is the cause.

When to see a doctor

See your doctor if you have felt tired for a few weeks and don’t know why, if it is affecting your daily life, or if you have other symptoms such as losing weight without trying. Tell them you are vegan, and ask whether a blood test for iron and B12 makes sense.

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